Index: Lib/pydoc.py
===================================================================
--- Lib/pydoc.py	(revision 86636)
+++ Lib/pydoc.py	(working copy)
@@ -1139,6 +1139,26 @@
                 push('    ' + makename(base))
             push('')
 
+        # List the built-in subclasses, if any:
+        subclasses = []
+        for attr, attrval in __builtins__.items():
+            if not attrval is object:
+                try:
+                    if issubclass(attrval, object):
+                        subclasses.append(attrval)
+                except TypeError:
+                    pass
+        for i in range(len(subclasses)-1, -1, -1):
+            if issubclass(subclasses[i], tuple(subclasses[:i]+subclasses[i+1:])):
+                del subclasses[i]
+                # This removes any subclass which is a child of some other subclass,
+                # i.e. keep only immediate child classes of "object", not grandchildren etc.
+        if subclasses:
+            push("Built-in subclasses:")
+            for subclassname in sorted([cls.__name__ for cls in subclasses]):
+                push('    ' + subclassname)
+            push('')
+
         # Cute little class to pump out a horizontal rule between sections.
         class HorizontalRule:
             def __init__(self):
Index: Lib/test/test_pydoc.py
===================================================================
--- Lib/test/test_pydoc.py	(revision 86636)
+++ Lib/test/test_pydoc.py	(working copy)
@@ -327,7 +327,94 @@
         self.assertEqual(stripid("<type 'exceptions.Exception'>"),
                          "<type 'exceptions.Exception'>")
 
+    def test_builtin_with_child(self):
+        """Tests help on builtin object which have only child classes.
 
+        When running help() on a builtin class which has child classes, it
+        should contain a "Built-in subclasses" section. For example:
+
+        >>> help(ArithmeticError)
+        Help on class ArithmeticError in module builtins:
+
+        class ArithmeticError(Exception)
+         |  Base class for arithmetic errors.
+         |
+         ...
+         |
+         |  Built-in subclasses:
+         |      FloatingPointError
+         |      OverflowError
+         |      ZeroDivisionError
+        """
+        doc = pydoc.TextDoc()
+        text = doc.docclass(ArithmeticError)
+        snip = (" |  Built-in subclasses:\n"
+                " |      FloatingPointError\n"
+                " |      OverflowError\n"
+                " |      ZeroDivisionError")
+        self.assertIn(snip, text)
+
+    def test_builtin_with_grandchild(self):
+        """Tests help on builtin classes which have grandchild classes.
+
+        When running help() on a builtin class which has child classes, it
+        should contain a "Built-in subclasses" section. However, if it also has
+        grandchildren, these should not show up on the subclasses section.
+        For example:
+
+        >>> help(Exception)
+        Help on class Exception in module builtins:
+
+        class Exception(BaseException)
+         |  Common base class for all non-exit exceptions.
+         |
+         ...
+         |
+         |  Built-in subclasses:
+         |      ArithmeticError
+         |      AssertionError
+         |      AttributeError
+         ...
+        """
+        doc = pydoc.TextDoc()
+        text = doc.docclass(Exception)
+        snip = (" |  Built-in subclasses:\n"
+                " |      ArithmeticError\n"
+                " |      AssertionError\n"
+                " |      AttributeError")
+        self.assertIn(snip, text)
+        # Testing that the grandchild ZeroDivisionError does not show up
+        self.assertNotIn('ZeroDivisionError', text)
+
+    def test_builtin_no_child(self):
+        """Tests help on builtin object which have no child classes.
+
+        When running help() on a builtin class which has no child classes, it
+        should not contain any "Built-in subclasses" section. For example:
+
+        >>> help(ZeroDivisionError)
+
+        Help on class ZeroDivisionError in module builtins:
+
+        class ZeroDivisionError(ArithmeticError)
+         |  Second argument to a division or modulo operation was zero.
+         |
+         |  Method resolution order:
+         |      ZeroDivisionError
+         |      ArithmeticError
+         |      Exception
+         |      BaseException
+         |      object
+         |
+         |  Methods defined here:
+         ...
+        """
+        doc = pydoc.TextDoc()
+        text = doc.docclass(ZeroDivisionError)
+        # Testing that the subclasses section does not appear
+        self.assertNotIn('Built-in subclasses', text)
+
+
 class TestDescriptions(unittest.TestCase):
 
     def test_module(self):