diff --git a/Doc/library/mmap.rst b/Doc/library/mmap.rst
index abe5b7b..0e982c1 100644
--- a/Doc/library/mmap.rst
+++ b/Doc/library/mmap.rst
@@ -40,7 +40,7 @@
    length.
 
 
-.. function:: mmap(fileno, length[, tagname[, access]])
+.. function:: mmap(fileno, length[, tagname[, access[, offset]]])
 
    **(Windows version)** Maps *length* bytes from the file specified by the file
    handle *fileno*, and returns a mmap object.  If *length* is larger than the
@@ -56,8 +56,12 @@
    the mapping is created without a name.  Avoiding the use of the tag parameter
    will assist in keeping your code portable between Unix and Windows.
 
+   *offset* may be specified as a non-negative integer offset. mmap references will 
+   be relative to the offset from the beginning of the file. *offset* defaults to 0.
+   *offset* must be a multiple of the ALLOCATIONGRANULARITY.
 
-.. function:: mmap(fileno, length[, flags[, prot[, access]]])
+
+.. function:: mmap(fileno, length[, flags[, prot[, access[, offset]]]])
    :noindex:
 
    **(Unix version)** Maps *length* bytes from the file specified by the file
@@ -79,6 +83,10 @@
    parameter.  It is an error to specify both *flags*, *prot* and *access*.  See
    the description of *access* above for information on how to use this parameter.
 
+   *offset* may be specified as a non-negative integer offset. mmap references will 
+   be relative to the offset from the beginning of the file. *offset* defaults to 0.
+   *offset* must be a multiple of the PAGESIZE or ALLOCATIONGRANULARITY.
+
 Memory-mapped file objects support the following methods:
 
 
@@ -171,3 +179,4 @@
    created with :const:`ACCESS_READ`, then writing to it will throw a
    :exc:`TypeError` exception.
 
+