diff --git a/Lib/fnmatch.py b/Lib/fnmatch.py
index 3bf2463..dd01205 100644
--- a/Lib/fnmatch.py
+++ b/Lib/fnmatch.py
@@ -37,15 +37,24 @@
     pat = os.path.normcase(pat)
     return fnmatchcase(name, pat)
 
+def _compile_pattern(pat):
+    regex = _cache.get(pat)
+    if regex is None:
+        if isinstance(pat, bytes):
+            pat_str = str(pat, 'ISO-8859-1')
+            res_str = translate(pat_str)
+            res = bytes(res_str, 'ISO-8859-1')
+        else:
+            res = translate(pat)
+        _cache[pat] = regex = re.compile(res)
+    return regex.match
+
 def filter(names, pat):
     """Return the subset of the list NAMES that match PAT"""
     import os,posixpath
-    result=[]
-    pat=os.path.normcase(pat)
-    if not pat in _cache:
-        res = translate(pat)
-        _cache[pat] = re.compile(res)
-    match=_cache[pat].match
+    result = []
+    pat = os.path.normcase(pat)
+    match = _compile_pattern(pat)
     if os.path is posixpath:
         # normcase on posix is NOP. Optimize it away from the loop.
         for name in names:
@@ -64,10 +73,8 @@
     its arguments.
     """
 
-    if not pat in _cache:
-        res = translate(pat)
-        _cache[pat] = re.compile(res)
-    return _cache[pat].match(name) is not None
+    match = _compile_pattern(pat)
+    return match(name) is not None
 
 def translate(pat):
     """Translate a shell PATTERN to a regular expression.
diff --git a/Lib/genericpath.py b/Lib/genericpath.py
index 73d7b26..41ad234 100644
--- a/Lib/genericpath.py
+++ b/Lib/genericpath.py
@@ -87,6 +87,7 @@
 
     Extension is everything from the last dot to the end, ignoring
     leading dots.  Returns "(root, ext)"; ext may be empty."""
+    # NOTE: This code must work for text and bytes strings.
 
     sepIndex = p.rfind(sep)
     if altsep:
@@ -98,8 +99,8 @@
         # skip all leading dots
         filenameIndex = sepIndex + 1
         while filenameIndex < dotIndex:
-            if p[filenameIndex] != extsep:
+            if p[filenameIndex:filenameIndex+1] != extsep:
                 return p[:dotIndex], p[dotIndex:]
             filenameIndex += 1
 
-    return p, ''
+    return p, p[:0]
diff --git a/Lib/glob.py b/Lib/glob.py
index cd6c302..9529f7e 100644
--- a/Lib/glob.py
+++ b/Lib/glob.py
@@ -27,7 +27,7 @@
         return
     dirname, basename = os.path.split(pathname)
     if not dirname:
-        for name in glob1(os.curdir, basename):
+        for name in glob1(None, basename):
             yield name
         return
     if has_magic(dirname):
@@ -48,10 +48,10 @@
 
 def glob1(dirname, pattern):
     if not dirname:
-        dirname = os.curdir
-    if isinstance(pattern, str) and not isinstance(dirname, str):
-        dirname = str(dirname, sys.getfilesystemencoding() or
-                                   sys.getdefaultencoding())
+        if isinstance(pattern, bytes):
+            dirname = bytes(os.curdir, 'ASCII')
+        else:
+            dirname = os.curdir
     try:
         names = os.listdir(dirname)
     except os.error:
@@ -73,6 +73,11 @@
 
 
 magic_check = re.compile('[*?[]')
+magic_check_bytes = re.compile(b'[*?[]')
 
 def has_magic(s):
-    return magic_check.search(s) is not None
+    if isinstance(s, bytes):
+        match = magic_check_bytes.search(s)
+    else:
+        match = magic_check.search(s)
+    return match is not None
diff --git a/Lib/io.py b/Lib/io.py
index c1513f5..8e65a10 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -82,14 +82,13 @@
 def open(file, mode="r", buffering=None, encoding=None, errors=None,
          newline=None, closefd=True):
 
-    r"""Open file and return a stream. If the file cannot be opened, an IOError is
-    raised.
+    r"""Open file and return a stream.  Raise IOError upon failure.
 
-    file is either a string giving the name (and the path if the file
-    isn't in the current working directory) of the file to be opened or an
-    integer file descriptor of the file to be wrapped. (If a file
-    descriptor is given, it is closed when the returned I/O object is
-    closed, unless closefd is set to False.)
+    file is either a text or byte string giving the name (and the path
+    if the file isn't in the current working directory) of the file to
+    be opened or an integer file descriptor of the file to be
+    wrapped. (If a file descriptor is given, it is closed when the
+    returned I/O object is closed, unless closefd is set to False.)
 
     mode is an optional string that specifies the mode in which the file
     is opened. It defaults to 'r' which means open for reading in text
@@ -180,7 +179,7 @@
     opened in a text mode, and for bytes a BytesIO can be used like a file
     opened in a binary mode.
     """
-    if not isinstance(file, (str, int)):
+    if not isinstance(file, (str, bytes, int)):
         raise TypeError("invalid file: %r" % file)
     if not isinstance(mode, str):
         raise TypeError("invalid mode: %r" % mode)
diff --git a/Lib/posixpath.py b/Lib/posixpath.py
index 575492f..745c920 100644
--- a/Lib/posixpath.py
+++ b/Lib/posixpath.py
@@ -11,6 +11,7 @@
 """
 
 import os
+import sys
 import stat
 import genericpath
 from genericpath import *
@@ -23,7 +24,8 @@
            "curdir","pardir","sep","pathsep","defpath","altsep","extsep",
            "devnull","realpath","supports_unicode_filenames","relpath"]
 
-# strings representing various path-related bits and pieces
+# Strings representing various path-related bits and pieces.
+# These are primarily for export; internally, they are hardcoded.
 curdir = '.'
 pardir = '..'
 extsep = '.'
@@ -33,6 +35,12 @@
 altsep = None
 devnull = '/dev/null'
 
+def _get_sep(path):
+    if isinstance(path, bytes):
+        return b'/'
+    else:
+        return '/'
+
 # Normalize the case of a pathname.  Trivial in Posix, string.lower on Mac.
 # On MS-DOS this may also turn slashes into backslashes; however, other
 # normalizations (such as optimizing '../' away) are not allowed
@@ -40,6 +48,7 @@
 
 def normcase(s):
     """Normalize case of pathname.  Has no effect under Posix"""
+    # TODO: on Mac OS X, this should really return s.lower().
     return s
 
 
@@ -48,7 +57,8 @@
 
 def isabs(s):
     """Test whether a path is absolute"""
-    return s.startswith('/')
+    sep = _get_sep(s)
+    return s.startswith(sep)
 
 
 # Join pathnames.
@@ -59,14 +69,15 @@
     """Join two or more pathname components, inserting '/' as needed.
     If any component is an absolute path, all previous path components
     will be discarded."""
+    sep = _get_sep(a)
     path = a
     for b in p:
-        if b.startswith('/'):
+        if b.startswith(sep):
             path = b
-        elif path == '' or path.endswith('/'):
+        elif not path or path.endswith(sep):
             path +=  b
         else:
-            path += '/' + b
+            path += sep + b
     return path
 
 
@@ -78,10 +89,11 @@
 def split(p):
     """Split a pathname.  Returns tuple "(head, tail)" where "tail" is
     everything after the final slash.  Either part may be empty."""
-    i = p.rfind('/') + 1
+    sep = _get_sep(p)
+    i = p.rfind(sep) + 1
     head, tail = p[:i], p[i:]
-    if head and head != '/'*len(head):
-        head = head.rstrip('/')
+    if head and head != sep*len(head):
+        head = head.rstrip(sep)
     return head, tail
 
 
@@ -91,7 +103,13 @@
 # It is always true that root + ext == p.
 
 def splitext(p):
-    return genericpath._splitext(p, sep, altsep, extsep)
+    if isinstance(p, bytes):
+        sep = b'/'
+        extsep = b'.'
+    else:
+        sep = '/'
+        extsep = '.'
+    return genericpath._splitext(p, sep, None, extsep)
 splitext.__doc__ = genericpath._splitext.__doc__
 
 # Split a pathname into a drive specification and the rest of the
@@ -100,14 +118,15 @@
 def splitdrive(p):
     """Split a pathname into drive and path. On Posix, drive is always
     empty."""
-    return '', p
+    return p[:0], p
 
 
 # Return the tail (basename) part of a path, same as split(path)[1].
 
 def basename(p):
     """Returns the final component of a pathname"""
-    i = p.rfind('/') + 1
+    sep = _get_sep(p)
+    i = p.rfind(sep) + 1
     return p[i:]
 
 
@@ -115,10 +134,11 @@
 
 def dirname(p):
     """Returns the directory component of a pathname"""
-    i = p.rfind('/') + 1
+    sep = _get_sep(p)
+    i = p.rfind(sep) + 1
     head = p[:i]
-    if head and head != '/'*len(head):
-        head = head.rstrip('/')
+    if head and head != sep*len(head):
+        head = head.rstrip(sep)
     return head
 
 
@@ -179,7 +199,11 @@
     """Test whether a path is a mount point"""
     try:
         s1 = os.lstat(path)
-        s2 = os.lstat(join(path, '..'))
+        if isinstance(path, bytes):
+            parent = join(path, b'..')
+        else:
+            parent = join(path, '..')
+        s2 = os.lstat(parent)
     except os.error:
         return False # It doesn't exist -- so not a mount point :-)
     dev1 = s1.st_dev
@@ -205,9 +229,14 @@
 def expanduser(path):
     """Expand ~ and ~user constructions.  If user or $HOME is unknown,
     do nothing."""
-    if not path.startswith('~'):
+    if isinstance(path, bytes):
+        tilde = b'~'
+    else:
+        tilde = '~'
+    if not path.startswith(tilde):
         return path
-    i = path.find('/', 1)
+    sep = _get_sep(path)
+    i = path.find(sep, 1)
     if i < 0:
         i = len(path)
     if i == 1:
@@ -218,12 +247,17 @@
             userhome = os.environ['HOME']
     else:
         import pwd
+        name = path[1:i]
+        if isinstance(name, bytes):
+            name = str(name, 'ASCII')
         try:
-            pwent = pwd.getpwnam(path[1:i])
+            pwent = pwd.getpwnam(name)
         except KeyError:
             return path
         userhome = pwent.pw_dir
-    userhome = userhome.rstrip('/')
+    if isinstance(path, bytes):
+        userhome = userhome.encode(sys.getfilesystemencoding())
+    userhome = userhome.rstrip(sep)
     return userhome + path[i:]
 
 
@@ -232,28 +266,47 @@
 # Non-existent variables are left unchanged.
 
 _varprog = None
+_varprogb = None
 
 def expandvars(path):
     """Expand shell variables of form $var and ${var}.  Unknown variables
     are left unchanged."""
-    global _varprog
-    if '$' not in path:
-        return path
-    if not _varprog:
-        import re
-        _varprog = re.compile(r'\$(\w+|\{[^}]*\})', re.ASCII)
+    global _varprog, _varprogb
+    if isinstance(path, bytes):
+        if b'$' not in path:
+            return path
+        if not _varprogb:
+            import re
+            _varprogb = re.compile(br'\$(\w+|\{[^}]*\})', re.ASCII)
+        search = _varprogb.search
+        start = b'{'
+        end = b'}'
+    else:
+        if '$' not in path:
+            return path
+        if not _varprog:
+            import re
+            _varprog = re.compile(r'\$(\w+|\{[^}]*\})', re.ASCII)
+        search = _varprog.search
+        start = '{'
+        end = '}'
     i = 0
     while True:
-        m = _varprog.search(path, i)
+        m = search(path, i)
         if not m:
             break
         i, j = m.span(0)
         name = m.group(1)
-        if name.startswith('{') and name.endswith('}'):
+        if name.startswith(start) and name.endswith(end):
             name = name[1:-1]
+        if isinstance(name, bytes):
+            name = str(name, 'ASCII')
         if name in os.environ:
             tail = path[j:]
-            path = path[:i] + os.environ[name]
+            value = os.environ[name]
+            if isinstance(path, bytes):
+                value = value.encode('ASCII')
+            path = path[:i] + value
             i = len(path)
             path += tail
         else:
@@ -267,35 +320,49 @@
 
 def normpath(path):
     """Normalize path, eliminating double slashes, etc."""
-    if path == '':
-        return '.'
-    initial_slashes = path.startswith('/')
+    if isinstance(path, bytes):
+        sep = b'/'
+        empty = b''
+        dot = b'.'
+        dotdot = b'..'
+    else:
+        sep = '/'
+        empty = ''
+        dot = '.'
+        dotdot = '..'
+    if path == empty:
+        return dot
+    initial_slashes = path.startswith(sep)
     # POSIX allows one or two initial slashes, but treats three or more
     # as single slash.
     if (initial_slashes and
-        path.startswith('//') and not path.startswith('///')):
+        path.startswith(sep*2) and not path.startswith(sep*3)):
         initial_slashes = 2
-    comps = path.split('/')
+    comps = path.split(sep)
     new_comps = []
     for comp in comps:
-        if comp in ('', '.'):
+        if comp in (empty, dot):
             continue
-        if (comp != '..' or (not initial_slashes and not new_comps) or
-             (new_comps and new_comps[-1] == '..')):
+        if (comp != dotdot or (not initial_slashes and not new_comps) or
+             (new_comps and new_comps[-1] == dotdot)):
             new_comps.append(comp)
         elif new_comps:
             new_comps.pop()
     comps = new_comps
-    path = '/'.join(comps)
+    path = sep.join(comps)
     if initial_slashes:
-        path = '/'*initial_slashes + path
-    return path or '.'
+        path = sep*initial_slashes + path
+    return path or dot
 
 
 def abspath(path):
     """Return an absolute path."""
     if not isabs(path):
-        path = join(os.getcwd(), path)
+        if isinstance(path, bytes):
+            cwd = os.getcwdb()
+        else:
+            cwd = os.getcwd()
+        path = join(cwd, path)
     return normpath(path)
 
 
@@ -305,10 +372,16 @@
 def realpath(filename):
     """Return the canonical path of the specified filename, eliminating any
 symbolic links encountered in the path."""
-    if isabs(filename):
-        bits = ['/'] + filename.split('/')[1:]
+    if isinstance(filename, bytes):
+        sep = b'/'
+        empty = b''
     else:
-        bits = [''] + filename.split('/')
+        sep = '/'
+        empty = ''
+    if isabs(filename):
+        bits = [sep] + filename.split(sep)[1:]
+    else:
+        bits = [empty] + filename.split(sep)
 
     for i in range(2, len(bits)+1):
         component = join(*bits[0:i])
@@ -347,12 +420,24 @@
 
 supports_unicode_filenames = False
 
-def relpath(path, start=curdir):
+def relpath(path, start=None):
     """Return a relative version of a path"""
 
     if not path:
         raise ValueError("no path specified")
 
+    if isinstance(path, bytes):
+        curdir = b'.'
+        sep = b'/'
+        pardir = b'..'
+    else:
+        curdir = '.'
+        sep = '/'
+        pardir = '..'
+
+    if start is None:
+        start = curdir
+
     start_list = abspath(start).split(sep)
     path_list = abspath(path).split(sep)
 
diff --git a/Lib/test/test_fnmatch.py b/Lib/test/test_fnmatch.py
index c593704..30ccf69 100644
--- a/Lib/test/test_fnmatch.py
+++ b/Lib/test/test_fnmatch.py
@@ -37,6 +37,15 @@
         check('a', r'[!\]')
         check('\\', r'[!\]', 0)
 
+    def test_mix_bytes_str(self):
+        self.assertRaises(TypeError, fnmatch, 'test', b'*')
+        self.assertRaises(TypeError, fnmatch, b'test', '*')
+        self.assertRaises(TypeError, fnmatchcase, 'test', b'*')
+        self.assertRaises(TypeError, fnmatchcase, b'test', '*')
+
+    def test_bytes(self):
+        self.check_match(b'test', b'te*')
+        self.check_match(b'test\xff', b'te*\xff')
 
 def test_main():
     support.run_unittest(FnmatchTestCase)
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 59f8c41..45decb7 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -29,7 +29,7 @@
     def testNoArgFunctions(self):
         # test posix functions which take no arguments and have
         # no side-effects which we need to cleanup (e.g., fork, wait, abort)
-        NO_ARG_FUNCTIONS = [ "ctermid", "getcwd", "getcwdu", "uname",
+        NO_ARG_FUNCTIONS = [ "ctermid", "getcwd", "getcwdb", "uname",
                              "times", "getloadavg",
                              "getegid", "geteuid", "getgid", "getgroups",
                              "getpid", "getpgrp", "getppid", "getuid",
diff --git a/Lib/test/test_posixpath.py b/Lib/test/test_posixpath.py
index 8a7dd72..3676e9f 100644
--- a/Lib/test/test_posixpath.py
+++ b/Lib/test/test_posixpath.py
@@ -31,20 +31,34 @@
     def test_normcase(self):
         # Check that normcase() is idempotent
         p = "FoO/./BaR"
-        p = posixpath.normcase(p)
+        self.assertEqual(p, posixpath.normcase(p))
+
+        p = b"FoO/./BaR"
         self.assertEqual(p, posixpath.normcase(p))
 
         self.assertRaises(TypeError, posixpath.normcase)
 
     def test_join(self):
-        self.assertEqual(posixpath.join("/foo", "bar", "/bar", "baz"), "/bar/baz")
+        self.assertEqual(posixpath.join("/foo", "bar", "/bar", "baz"),
+                         "/bar/baz")
         self.assertEqual(posixpath.join("/foo", "bar", "baz"), "/foo/bar/baz")
-        self.assertEqual(posixpath.join("/foo/", "bar/", "baz/"), "/foo/bar/baz/")
+        self.assertEqual(posixpath.join("/foo/", "bar/", "baz/"),
+                         "/foo/bar/baz/")
+
+        self.assertEqual(posixpath.join(b"/foo", b"bar", b"/bar", b"baz"),
+                         b"/bar/baz")
+        self.assertEqual(posixpath.join(b"/foo", b"bar", b"baz"),
+                         b"/foo/bar/baz")
+        self.assertEqual(posixpath.join(b"/foo/", b"bar/", b"baz/"),
+                         b"/foo/bar/baz/")
 
         self.assertRaises(TypeError, posixpath.join)
+        self.assertRaises(TypeError, posixpath.join, b"bytes", "str")
+        self.assertRaises(TypeError, posixpath.join, "str", b"bytes")
 
     def test_splitdrive(self):
         self.assertEqual(posixpath.splitdrive("/foo/bar"), ("", "/foo/bar"))
+        self.assertEqual(posixpath.splitdrive(b"/foo/bar"), (b"", b"/foo/bar"))
 
         self.assertRaises(TypeError, posixpath.splitdrive)
 
@@ -55,15 +69,41 @@
         self.assertEqual(posixpath.split("////foo"), ("////", "foo"))
         self.assertEqual(posixpath.split("//foo//bar"), ("//foo", "bar"))
 
+        self.assertEqual(posixpath.split(b"/foo/bar"), (b"/foo", b"bar"))
+        self.assertEqual(posixpath.split(b"/"), (b"/", b""))
+        self.assertEqual(posixpath.split(b"foo"), (b"", b"foo"))
+        self.assertEqual(posixpath.split(b"////foo"), (b"////", b"foo"))
+        self.assertEqual(posixpath.split(b"//foo//bar"), (b"//foo", b"bar"))
+
         self.assertRaises(TypeError, posixpath.split)
 
     def splitextTest(self, path, filename, ext):
         self.assertEqual(posixpath.splitext(path), (filename, ext))
         self.assertEqual(posixpath.splitext("/" + path), ("/" + filename, ext))
-        self.assertEqual(posixpath.splitext("abc/" + path), ("abc/" + filename, ext))
-        self.assertEqual(posixpath.splitext("abc.def/" + path), ("abc.def/" + filename, ext))
-        self.assertEqual(posixpath.splitext("/abc.def/" + path), ("/abc.def/" + filename, ext))
-        self.assertEqual(posixpath.splitext(path + "/"), (filename + ext + "/", ""))
+        self.assertEqual(posixpath.splitext("abc/" + path),
+                         ("abc/" + filename, ext))
+        self.assertEqual(posixpath.splitext("abc.def/" + path),
+                         ("abc.def/" + filename, ext))
+        self.assertEqual(posixpath.splitext("/abc.def/" + path),
+                         ("/abc.def/" + filename, ext))
+        self.assertEqual(posixpath.splitext(path + "/"),
+                         (filename + ext + "/", ""))
+
+        path = bytes(path, "ASCII")
+        filename = bytes(filename, "ASCII")
+        ext = bytes(ext, "ASCII")
+
+        self.assertEqual(posixpath.splitext(path), (filename, ext))
+        self.assertEqual(posixpath.splitext(b"/" + path),
+                         (b"/" + filename, ext))
+        self.assertEqual(posixpath.splitext(b"abc/" + path),
+                         (b"abc/" + filename, ext))
+        self.assertEqual(posixpath.splitext(b"abc.def/" + path),
+                         (b"abc.def/" + filename, ext))
+        self.assertEqual(posixpath.splitext(b"/abc.def/" + path),
+                         (b"/abc.def/" + filename, ext))
+        self.assertEqual(posixpath.splitext(path + b"/"),
+                         (filename + ext + b"/", b""))
 
     def test_splitext(self):
         self.splitextTest("foo.bar", "foo", ".bar")
@@ -87,13 +127,14 @@
         self.assertIs(posixpath.isabs("/foo/bar"), True)
         self.assertIs(posixpath.isabs("foo/bar"), False)
 
+        self.assertIs(posixpath.isabs(b""), False)
+        self.assertIs(posixpath.isabs(b"/"), True)
+        self.assertIs(posixpath.isabs(b"/foo"), True)
+        self.assertIs(posixpath.isabs(b"/foo/bar"), True)
+        self.assertIs(posixpath.isabs(b"foo/bar"), False)
+
         self.assertRaises(TypeError, posixpath.isabs)
 
-    def test_splitdrive(self):
-        self.assertEqual(posixpath.splitdrive("/foo/bar"), ("", "/foo/bar"))
-
-        self.assertRaises(TypeError, posixpath.splitdrive)
-
     def test_basename(self):
         self.assertEqual(posixpath.basename("/foo/bar"), "bar")
         self.assertEqual(posixpath.basename("/"), "")
@@ -101,6 +142,12 @@
         self.assertEqual(posixpath.basename("////foo"), "foo")
         self.assertEqual(posixpath.basename("//foo//bar"), "bar")
 
+        self.assertEqual(posixpath.basename(b"/foo/bar"), b"bar")
+        self.assertEqual(posixpath.basename(b"/"), b"")
+        self.assertEqual(posixpath.basename(b"foo"), b"foo")
+        self.assertEqual(posixpath.basename(b"////foo"), b"foo")
+        self.assertEqual(posixpath.basename(b"//foo//bar"), b"bar")
+
         self.assertRaises(TypeError, posixpath.basename)
 
     def test_dirname(self):
@@ -110,6 +157,12 @@
         self.assertEqual(posixpath.dirname("////foo"), "////")
         self.assertEqual(posixpath.dirname("//foo//bar"), "//foo")
 
+        self.assertEqual(posixpath.dirname(b"/foo/bar"), b"/foo")
+        self.assertEqual(posixpath.dirname(b"/"), b"/")
+        self.assertEqual(posixpath.dirname(b"foo"), b"")
+        self.assertEqual(posixpath.dirname(b"////foo"), b"////")
+        self.assertEqual(posixpath.dirname(b"//foo//bar"), b"//foo")
+
         self.assertRaises(TypeError, posixpath.dirname)
 
     def test_commonprefix(self):
@@ -130,6 +183,19 @@
             "/home/swen/spam"
         )
 
+        self.assertEqual(
+            posixpath.commonprefix([b"/home/swenson/spam", b"/home/swen/spam"]),
+            b"/home/swen"
+        )
+        self.assertEqual(
+            posixpath.commonprefix([b"/home/swen/spam", b"/home/swen/eggs"]),
+            b"/home/swen/"
+        )
+        self.assertEqual(
+            posixpath.commonprefix([b"/home/swen/spam", b"/home/swen/spam"]),
+            b"/home/swen/spam"
+        )
+
         testlist = ['', 'abc', 'Xbcd', 'Xb', 'XY', 'abcd', 'aXc', 'abd', 'ab', 'aX', 'abcX']
         for s1 in testlist:
             for s2 in testlist:
@@ -330,20 +396,28 @@
 
     def test_expanduser(self):
         self.assertEqual(posixpath.expanduser("foo"), "foo")
+        self.assertEqual(posixpath.expanduser(b"foo"), b"foo")
         try:
             import pwd
         except ImportError:
             pass
         else:
             self.assert_(isinstance(posixpath.expanduser("~/"), str))
+            self.assert_(isinstance(posixpath.expanduser(b"~/"), bytes))
             # if home directory == root directory, this test makes no sense
             if posixpath.expanduser("~") != '/':
                 self.assertEqual(
                     posixpath.expanduser("~") + "/",
                     posixpath.expanduser("~/")
                 )
+                self.assertEqual(
+                    posixpath.expanduser(b"~") + b"/",
+                    posixpath.expanduser(b"~/")
+                )
             self.assert_(isinstance(posixpath.expanduser("~root/"), str))
             self.assert_(isinstance(posixpath.expanduser("~foo/"), str))
+            self.assert_(isinstance(posixpath.expanduser(b"~root/"), bytes))
+            self.assert_(isinstance(posixpath.expanduser(b"~foo/"), bytes))
 
         self.assertRaises(TypeError, posixpath.expanduser)
 
@@ -366,6 +440,19 @@
             self.assertEqual(posixpath.expandvars("${{foo}}"), "baz1}")
             self.assertEqual(posixpath.expandvars("$foo$foo"), "barbar")
             self.assertEqual(posixpath.expandvars("$bar$bar"), "$bar$bar")
+
+            self.assertEqual(posixpath.expandvars(b"foo"), b"foo")
+            self.assertEqual(posixpath.expandvars(b"$foo bar"), b"bar bar")
+            self.assertEqual(posixpath.expandvars(b"${foo}bar"), b"barbar")
+            self.assertEqual(posixpath.expandvars(b"$[foo]bar"), b"$[foo]bar")
+            self.assertEqual(posixpath.expandvars(b"$bar bar"), b"$bar bar")
+            self.assertEqual(posixpath.expandvars(b"$?bar"), b"$?bar")
+            self.assertEqual(posixpath.expandvars(b"${foo}bar"), b"barbar")
+            self.assertEqual(posixpath.expandvars(b"$foo}bar"), b"bar}bar")
+            self.assertEqual(posixpath.expandvars(b"${foo"), b"${foo")
+            self.assertEqual(posixpath.expandvars(b"${{foo}}"), b"baz1}")
+            self.assertEqual(posixpath.expandvars(b"$foo$foo"), b"barbar")
+            self.assertEqual(posixpath.expandvars(b"$bar$bar"), b"$bar$bar")
         finally:
             os.environ.clear()
             os.environ.update(oldenv)
@@ -378,18 +465,31 @@
         self.assertEqual(posixpath.normpath("//"), "//")
         self.assertEqual(posixpath.normpath("///"), "/")
         self.assertEqual(posixpath.normpath("///foo/.//bar//"), "/foo/bar")
-        self.assertEqual(posixpath.normpath("///foo/.//bar//.//..//.//baz"), "/foo/baz")
+        self.assertEqual(posixpath.normpath("///foo/.//bar//.//..//.//baz"),
+                         "/foo/baz")
         self.assertEqual(posixpath.normpath("///..//./foo/.//bar"), "/foo/bar")
 
+        self.assertEqual(posixpath.normpath(b""), b".")
+        self.assertEqual(posixpath.normpath(b"/"), b"/")
+        self.assertEqual(posixpath.normpath(b"//"), b"//")
+        self.assertEqual(posixpath.normpath(b"///"), b"/")
+        self.assertEqual(posixpath.normpath(b"///foo/.//bar//"), b"/foo/bar")
+        self.assertEqual(posixpath.normpath(b"///foo/.//bar//.//..//.//baz"),
+                         b"/foo/baz")
+        self.assertEqual(posixpath.normpath(b"///..//./foo/.//bar"),
+                         b"/foo/bar")
+
         self.assertRaises(TypeError, posixpath.normpath)
 
     def test_abspath(self):
         self.assert_("foo" in posixpath.abspath("foo"))
+        self.assert_(b"foo" in posixpath.abspath(b"foo"))
 
         self.assertRaises(TypeError, posixpath.abspath)
 
     def test_realpath(self):
         self.assert_("foo" in realpath("foo"))
+        self.assert_(b"foo" in realpath(b"foo"))
         self.assertRaises(TypeError, posixpath.realpath)
 
     if hasattr(os, "symlink"):
@@ -499,12 +599,34 @@
             self.assertEqual(posixpath.relpath("a/b"), "a/b")
             self.assertEqual(posixpath.relpath("../a/b"), "../a/b")
             self.assertEqual(posixpath.relpath("a", "../b"), "../"+curdir+"/a")
-            self.assertEqual(posixpath.relpath("a/b", "../c"), "../"+curdir+"/a/b")
+            self.assertEqual(posixpath.relpath("a/b", "../c"),
+                             "../"+curdir+"/a/b")
             self.assertEqual(posixpath.relpath("a", "b/c"), "../../a")
             self.assertEqual(posixpath.relpath("a", "a"), ".")
         finally:
             os.getcwd = real_getcwd
 
+    def test_relpath_bytes(self):
+        (real_getcwdb, os.getcwdb) = (os.getcwdb, lambda: br"/home/user/bar")
+        try:
+            curdir = os.path.split(os.getcwdb())[-1]
+            self.assertRaises(ValueError, posixpath.relpath, b"")
+            self.assertEqual(posixpath.relpath(b"a"), b"a")
+            self.assertEqual(posixpath.relpath(posixpath.abspath(b"a")), b"a")
+            self.assertEqual(posixpath.relpath(b"a/b"), b"a/b")
+            self.assertEqual(posixpath.relpath(b"../a/b"), b"../a/b")
+            self.assertEqual(posixpath.relpath(b"a", b"../b"),
+                             b"../"+curdir+b"/a")
+            self.assertEqual(posixpath.relpath(b"a/b", b"../c"),
+                             b"../"+curdir+b"/a/b")
+            self.assertEqual(posixpath.relpath(b"a", b"b/c"), b"../../a")
+            self.assertEqual(posixpath.relpath(b"a", b"a"), b".")
+
+            self.assertRaises(TypeError, posixpath.relpath, b"bytes", "str")
+            self.assertRaises(TypeError, posixpath.relpath, "str", b"bytes")
+        finally:
+            os.getcwdb = real_getcwdb
+
 def test_main():
     support.run_unittest(PosixPathTest)
 
diff --git a/Lib/test/test_unicode_file.py b/Lib/test/test_unicode_file.py
index cc670db..9caadd8 100644
--- a/Lib/test/test_unicode_file.py
+++ b/Lib/test/test_unicode_file.py
@@ -90,7 +90,7 @@
         os.unlink(filename1 + ".new")
 
     def _do_directory(self, make_name, chdir_name, encoded):
-        cwd = os.getcwd()
+        cwd = os.getcwdb()
         if os.path.isdir(make_name):
             os.rmdir(make_name)
         os.mkdir(make_name)
@@ -98,10 +98,10 @@
             os.chdir(chdir_name)
             try:
                 if not encoded:
-                    cwd_result = os.getcwdu()
+                    cwd_result = os.getcwd()
                     name_result = make_name
                 else:
-                    cwd_result = os.getcwd().decode(TESTFN_ENCODING)
+                    cwd_result = os.getcwdb().decode(TESTFN_ENCODING)
                     name_result = make_name.decode(TESTFN_ENCODING)
 
                 cwd_result = unicodedata.normalize("NFD", cwd_result)
diff --git a/Misc/NEWS b/Misc/NEWS
index 51206bd..9e04767 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -4,8 +4,11 @@
 
 (editors: check NEWS.help for information about editing NEWS using ReST.)
 
-What's New in Python 3.0 release candidate 2
-============================================
+What's New in Python 3.0 beta 5
+===============================
+
+[Note: due to the number of unresolved issues we're going back to beta
+ releases for a while.]
 
 *Release date: XX-XXX-2008*
 
@@ -22,6 +25,9 @@
 Library
 -------
 
+- Issue #3187: Better support for "undecodable" filenames.  Code by Victor
+  Stinner, with small tweaks by GvR.
+
 - Issue #3965: Allow repeated calls to turtle.Screen, by making it a
   true singleton object.
 
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index f6a4d95..03959f7 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -1968,63 +1968,18 @@
 
 
 #ifdef HAVE_GETCWD
-PyDoc_STRVAR(posix_getcwd__doc__,
-"getcwd() -> path\n\n\
-Return a string representing the current working directory.");
-
 static PyObject *
-posix_getcwd(PyObject *self, PyObject *noargs)
-{
-	int bufsize_incr = 1024;
-	int bufsize = 0;
-	char *tmpbuf = NULL;
-	char *res = NULL;
-	PyObject *dynamic_return;
-
-	Py_BEGIN_ALLOW_THREADS
-	do {
-		bufsize = bufsize + bufsize_incr;
-		tmpbuf = malloc(bufsize);
-		if (tmpbuf == NULL) {
-			break;
-		}
-#if defined(PYOS_OS2) && defined(PYCC_GCC)
-		res = _getcwd2(tmpbuf, bufsize);
-#else
-		res = getcwd(tmpbuf, bufsize);
-#endif
-
-		if (res == NULL) {
-			free(tmpbuf);
-		}
-	} while ((res == NULL) && (errno == ERANGE));
-	Py_END_ALLOW_THREADS
-
-	if (res == NULL)
-		return posix_error();
-
-	dynamic_return = PyUnicode_FromString(tmpbuf);
-	free(tmpbuf);
-
-	return dynamic_return;
-}
-
-PyDoc_STRVAR(posix_getcwdu__doc__,
-"getcwdu() -> path\n\n\
-Return a unicode string representing the current working directory.");
-
-static PyObject *
-posix_getcwdu(PyObject *self, PyObject *noargs)
+posix_getcwd(int use_bytes)
 {
 	char buf[1026];
 	char *res;
 
 #ifdef Py_WIN_WIDE_FILENAMES
-	DWORD len;
-	if (unicode_file_names()) {
+	if (!use_bytes && unicode_file_names()) {
 		wchar_t wbuf[1026];
 		wchar_t *wbuf2 = wbuf;
 		PyObject *resobj;
+		DWORD len;
 		Py_BEGIN_ALLOW_THREADS
 		len = GetCurrentDirectoryW(sizeof wbuf/ sizeof wbuf[0], wbuf);
 		/* If the buffer is large enough, len does not include the
@@ -2059,8 +2014,30 @@
 	Py_END_ALLOW_THREADS
 	if (res == NULL)
 		return posix_error();
+	if (use_bytes)
+		return PyBytes_FromStringAndSize(buf, strlen(buf));
 	return PyUnicode_Decode(buf, strlen(buf), Py_FileSystemDefaultEncoding,"strict");
 }
+
+PyDoc_STRVAR(posix_getcwd__doc__,
+"getcwd() -> path\n\n\
+Return a unicode string representing the current working directory.");
+
+static PyObject *
+posix_getcwd_unicode(PyObject *self)
+{
+    return posix_getcwd(0);
+}
+
+PyDoc_STRVAR(posix_getcwdb__doc__,
+"getcwdb() -> path\n\n\
+Return a bytes string representing the current working directory.");
+
+static PyObject *
+posix_getcwd_bytes(PyObject *self)
+{
+    return posix_getcwd(1);
+}
 #endif
 
 
@@ -2378,9 +2355,12 @@
 				v = w;
 			}
 			else {
-				/* fall back to the original byte string, as
-				   discussed in patch #683592 */
+				/* Ignore undecodable filenames, as discussed
+				 * in issue 3187. To include these,
+				 * use getcwdb(). */
 				PyErr_Clear();
+				Py_DECREF(v);
+				continue;
 			}
 		}
 		if (PyList_Append(d, v) != 0) {
@@ -4477,9 +4457,7 @@
 			v = w;
 		}
 		else {
-			/* fall back to the original byte string, as
-			   discussed in patch #683592 */
-			PyErr_Clear();
+			v = NULL;
 		}
 	}
 	return v;
@@ -6810,8 +6788,10 @@
 	{"ctermid",	posix_ctermid, METH_NOARGS, posix_ctermid__doc__},
 #endif
 #ifdef HAVE_GETCWD
-	{"getcwd",	posix_getcwd, METH_NOARGS, posix_getcwd__doc__},
-	{"getcwdu",	posix_getcwdu, METH_NOARGS, posix_getcwdu__doc__},
+	{"getcwd",	(PyCFunction)posix_getcwd_unicode,
+	METH_NOARGS, posix_getcwd__doc__},
+	{"getcwdb",	(PyCFunction)posix_getcwd_bytes,
+	METH_NOARGS, posix_getcwdb__doc__},
 #endif
 #ifdef HAVE_LINK
 	{"link",	posix_link, METH_VARARGS, posix_link__doc__},