diff --git a/Lib/test/test_iter.py b/Lib/test/test_iter.py
index 3563661..c87f5ec 100644
--- a/Lib/test/test_iter.py
+++ b/Lib/test/test_iter.py
@@ -351,4 +351,39 @@
             except OSError:
                 pass
 
+    # Test map()'s use of iterators.
+    def test_builtin_map(self):
+        self.assertEqual(map(None, SequenceClass(5)), range(5))
+        self.assertEqual(map(lambda x: x+1, SequenceClass(5)), range(1, 6))
+
+        d = {"one": 1, "two": 2, "three": 3}
+        self.assertEqual(map(None, d), d.keys())
+        self.assertEqual(map(lambda k, d=d: (k, d[k]), d), d.items())
+        dkeys = d.keys()
+        expected = [(i < len(d) and dkeys[i] or None,
+                     i,
+                     i < len(d) and dkeys[i] or None)
+                    for i in range(5)]
+        self.assertEqual(map(None, d,
+                                   SequenceClass(5),
+                                   iter(d.iterkeys())),
+                         expected) 
+
+        f = open(TESTFN, "w")
+        try:
+            for i in range(10):
+                f.write("xy" * i + "\n") # line i has len 2*i+1
+        finally:
+            f.close()
+        f = open(TESTFN, "r")
+        try:
+            self.assertEqual(map(len, f), range(1, 21, 2))
+            f.seek(0, 0)
+        finally:
+            f.close()
+            try:
+                unlink(TESTFN)
+            except OSError:
+                pass
+
 run_unittest(TestCase)
diff --git a/Misc/NEWS b/Misc/NEWS
index 9d84845..617146c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -19,6 +19,7 @@
   arguments:
     filter()
     list()
+    map()
     max()
     min()
 
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 9e8a227..0c20d10 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -936,9 +936,8 @@
 builtin_map(PyObject *self, PyObject *args)
 {
 	typedef struct {
-		PyObject *seq;
-		PySequenceMethods *sqf;
-		int saw_IndexError;
+		PyObject *it;	/* the iterator object */
+		int saw_StopIteration;  /* bool:  did the iterator end? */
 	} sequence;
 
 	PyObject *func, *result;
@@ -961,104 +960,105 @@
 		return PySequence_List(PyTuple_GetItem(args, 1));
 	}
 
+	/* Get space for sequence descriptors.  Must NULL out the iterator
+	 * pointers so that jumping to Fail_2 later doesn't see trash.
+	 */
 	if ((seqs = PyMem_NEW(sequence, n)) == NULL) {
 		PyErr_NoMemory();
-		goto Fail_2;
+		return NULL;
+	}
+	for (i = 0; i < n; ++i) {
+		seqs[i].it = (PyObject*)NULL;
+		seqs[i].saw_StopIteration = 0;
 	}
 
-	/* Do a first pass to (a) verify the args are sequences; (b) set
-	 * len to the largest of their lengths; (c) initialize the seqs
-	 * descriptor vector.
+	/* Do a first pass to obtain iterators for the arguments, and set len
+	 * to the largest of their lengths.
 	 */
-	for (len = 0, i = 0, sqp = seqs; i < n; ++i, ++sqp) {
+	len = 0;
+	for (i = 0, sqp = seqs; i < n; ++i, ++sqp) {
+		PyObject *curseq;
 		int curlen;
-		PySequenceMethods *sqf;
 
-		if ((sqp->seq = PyTuple_GetItem(args, i + 1)) == NULL)
-			goto Fail_2;
-
-		sqp->saw_IndexError = 0;
-
-		sqp->sqf = sqf = sqp->seq->ob_type->tp_as_sequence;
-		if (sqf == NULL ||
-		    sqf->sq_item == NULL)
-		{
+		/* Get iterator. */
+		curseq = PyTuple_GetItem(args, i+1);
+		sqp->it = PyObject_GetIter(curseq);
+		if (sqp->it == NULL) {
 			static char errmsg[] =
-			    "argument %d to map() must be a sequence object";
+			    "argument %d to map() must support iteration";
 			char errbuf[sizeof(errmsg) + 25];
-
 			sprintf(errbuf, errmsg, i+2);
 			PyErr_SetString(PyExc_TypeError, errbuf);
 			goto Fail_2;
 		}
 
-		if (sqf->sq_length == NULL)
-			/* doesn't matter -- make something up */
-			curlen = 8;
-		else
-			curlen = (*sqf->sq_length)(sqp->seq);
+		/* Update len. */
+		curlen = -1;  /* unknown */
+		if (PySequence_Check(curseq) &&
+		    curseq->ob_type->tp_as_sequence->sq_length) {
+			curlen = PySequence_Size(curseq);
+			if (curlen < 0)
+				PyErr_Clear();
+		}
 		if (curlen < 0)
-			goto Fail_2;
+			curlen = 8;  /* arbitrary */
 		if (curlen > len)
 			len = curlen;
 	}
 
+	/* Get space for the result list. */
 	if ((result = (PyObject *) PyList_New(len)) == NULL)
 		goto Fail_2;
 
-	/* Iterate over the sequences until all have raised IndexError. */
+	/* Iterate over the sequences until all have stopped. */
 	for (i = 0; ; ++i) {
 		PyObject *alist, *item=NULL, *value;
-		int any = 0;
+		int numactive = 0;
 
 		if (func == Py_None && n == 1)
 			alist = NULL;
-		else {
-			if ((alist = PyTuple_New(n)) == NULL)
-				goto Fail_1;
-		}
+		else if ((alist = PyTuple_New(n)) == NULL)
+			goto Fail_1;
 
 		for (j = 0, sqp = seqs; j < n; ++j, ++sqp) {
-			if (sqp->saw_IndexError) {
+			if (sqp->saw_StopIteration) {
 				Py_INCREF(Py_None);
 				item = Py_None;
 			}
 			else {
-				item = (*sqp->sqf->sq_item)(sqp->seq, i);
-				if (item == NULL) {
-					if (PyErr_ExceptionMatches(
-						PyExc_IndexError))
-					{
-						PyErr_Clear();
-						Py_INCREF(Py_None);
-						item = Py_None;
-						sqp->saw_IndexError = 1;
+				item = PyIter_Next(sqp->it);
+				if (item)
+					++numactive;
+				else {
+					/* StopIteration is *implied* by a
+					 * NULL return from PyIter_Next() if
+					 * PyErr_Occurred() is false.
+					 */
+					if (PyErr_Occurred()) {
+						if (PyErr_ExceptionMatches(
+						    PyExc_StopIteration))
+							PyErr_Clear();
+						else {
+							Py_XDECREF(alist);
+							goto Fail_1;
+						}
 					}
-					else {
-						goto Fail_0;
-					}
+					Py_INCREF(Py_None);
+					item = Py_None;
+					sqp->saw_StopIteration = 1;
 				}
-				else
-					any = 1;
 
 			}
-			if (!alist)
+			if (alist)
+				PyTuple_SET_ITEM(alist, j, item);
+			else
 				break;
-			if (PyTuple_SetItem(alist, j, item) < 0) {
-				Py_DECREF(item);
-				goto Fail_0;
-			}
-			continue;
-
-		Fail_0:
-			Py_XDECREF(alist);
-			goto Fail_1;
 		}
 
 		if (!alist)
 			alist = item;
 
-		if (!any) {
+		if (numactive == 0) {
 			Py_DECREF(alist);
 			break;
 		}
@@ -1077,23 +1077,25 @@
 			if (status < 0)
 				goto Fail_1;
 		}
-		else {
-			if (PyList_SetItem(result, i, value) < 0)
-				goto Fail_1;
-		}
+		else if (PyList_SetItem(result, i, value) < 0)
+		 	goto Fail_1;
 	}
 
 	if (i < len && PyList_SetSlice(result, i, len, NULL) < 0)
 		goto Fail_1;
 
-	PyMem_DEL(seqs);
-	return result;
+	goto Succeed;
 
 Fail_1:
 	Py_DECREF(result);
 Fail_2:
-	if (seqs) PyMem_DEL(seqs);
-	return NULL;
+	result = NULL;
+Succeed:
+	assert(seqs);
+	for (i = 0; i < n; ++i)
+		Py_XDECREF(seqs[i].it);
+	PyMem_DEL(seqs);
+	return result;
 }
 
 static char map_doc[] =