Index: Doc/library/base64.rst
===================================================================
--- Doc/library/base64.rst	(revision 71822)
+++ Doc/library/base64.rst	(working copy)
@@ -128,10 +128,10 @@
    ``input.read()`` returns an empty string.
 
 
-.. function:: decodestring(s)
+.. function:: decodebytes(s)
 
-   Decode the string *s*, which must contain one or more lines of base64 encoded
-   data, and return a string containing the resulting binary data.
+   Decode the bytes *s*, which must contain one or more lines of base64 encoded
+   data, and return a bytes containing the resulting binary data.
 
 
 .. function:: encode(input, output)
@@ -143,11 +143,11 @@
    data plus a trailing newline character (``'\n'``).
 
 
-.. function:: encodestring(s)
+.. function:: encodebytes(s)
 
-   Encode the string *s*, which can contain arbitrary binary data, and return a
-   string containing one or more lines of base64-encoded data.
-   :func:`encodestring` returns a string containing one or more lines of
+   Encode the bytes *s*, which can contain arbitrary binary data, and return a
+   bytes containing one or more lines of base64-encoded data.
+   :func:`encodestring` returns a bytes containing one or more lines of
    base64-encoded data always including an extra trailing newline (``'\n'``).
 
 An example usage of the module:
Index: Lib/base64.py
===================================================================
--- Lib/base64.py	(revision 71822)
+++ Lib/base64.py	(working copy)
@@ -329,8 +329,8 @@
         output.write(s)
 
 
-def encodestring(s):
-    """Encode a string into multiple lines of base-64 data.
+def encodebytes(s):
+    """Encode bytes into multiple lines of base-64 data.
 
     Argument and return value are bytes.
     """
@@ -342,16 +342,21 @@
         pieces.append(binascii.b2a_base64(chunk))
     return b"".join(pieces)
 
+# For historical reasons
+encodestring = encodebytes
 
-def decodestring(s):
-    """Decode a string.
 
+def decodebytes(s):
+    """Decode bytes of base-64 encoded data.
+
     Argument and return value are bytes.
     """
     if not isinstance(s, bytes_types):
         raise TypeError("expected bytes, not %s" % s.__class__.__name__)
     return binascii.a2b_base64(s)
 
+# For historical reasons
+decodestring = decodebytes
 
 
 # Usable as a script...
Index: Lib/test/test_base64.py
===================================================================
--- Lib/test/test_base64.py	(revision 71822)
+++ Lib/test/test_base64.py	(working copy)
@@ -6,35 +6,37 @@
 
 
 class LegacyBase64TestCase(unittest.TestCase):
-    def test_encodestring(self):
+    def test_encodebytes(self):
         eq = self.assertEqual
-        eq(base64.encodestring(b"www.python.org"), b"d3d3LnB5dGhvbi5vcmc=\n")
-        eq(base64.encodestring(b"a"), b"YQ==\n")
-        eq(base64.encodestring(b"ab"), b"YWI=\n")
-        eq(base64.encodestring(b"abc"), b"YWJj\n")
-        eq(base64.encodestring(b""), b"")
-        eq(base64.encodestring(b"abcdefghijklmnopqrstuvwxyz"
+        eq(base64.encodebytes(b"www.python.org"), b"d3d3LnB5dGhvbi5vcmc=\n")
+        eq(base64.encodebytes(b"a"), b"YQ==\n")
+        eq(base64.encodebytes(b"ab"), b"YWI=\n")
+        eq(base64.encodebytes(b"abc"), b"YWJj\n")
+        eq(base64.encodebytes(b""), b"")
+        eq(base64.encodebytes(b"abcdefghijklmnopqrstuvwxyz"
                                b"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                b"0123456789!@#0^&*();:<>,. []{}"),
            b"YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eXpBQkNE"
            b"RUZHSElKS0xNTk9QUVJTVFVWV1hZWjAxMjM0\nNT"
            b"Y3ODkhQCMwXiYqKCk7Ojw+LC4gW117fQ==\n")
-        self.assertRaises(TypeError, base64.encodestring, "")
+        self.assertRaises(TypeError, base64.encodebytes, "")
+        eq(base64.encodestring(b"www.python.org"), b"d3d3LnB5dGhvbi5vcmc=\n")
 
-    def test_decodestring(self):
+    def test_decodebytes(self):
         eq = self.assertEqual
-        eq(base64.decodestring(b"d3d3LnB5dGhvbi5vcmc=\n"), b"www.python.org")
-        eq(base64.decodestring(b"YQ==\n"), b"a")
-        eq(base64.decodestring(b"YWI=\n"), b"ab")
-        eq(base64.decodestring(b"YWJj\n"), b"abc")
-        eq(base64.decodestring(b"YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eXpBQkNE"
+        eq(base64.decodebytes(b"d3d3LnB5dGhvbi5vcmc=\n"), b"www.python.org")
+        eq(base64.decodebytes(b"YQ==\n"), b"a")
+        eq(base64.decodebytes(b"YWI=\n"), b"ab")
+        eq(base64.decodebytes(b"YWJj\n"), b"abc")
+        eq(base64.decodebytes(b"YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eXpBQkNE"
                                b"RUZHSElKS0xNTk9QUVJTVFVWV1hZWjAxMjM0\nNT"
                                b"Y3ODkhQCMwXiYqKCk7Ojw+LC4gW117fQ==\n"),
            b"abcdefghijklmnopqrstuvwxyz"
            b"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
            b"0123456789!@#0^&*();:<>,. []{}")
-        eq(base64.decodestring(b''), b'')
-        self.assertRaises(TypeError, base64.decodestring, "")
+        eq(base64.decodebytes(b''), b'')
+        self.assertRaises(TypeError, base64.decodebytes, "")
+        eq(base64.decodestring(b"d3d3LnB5dGhvbi5vcmc=\n"), b"www.python.org")
 
     def test_encode(self):
         eq = self.assertEqual