Index: include/bits/basic_string.h
===================================================================
--- include/bits/basic_string.h	(revision 179472)
+++ include/bits/basic_string.h	(working copy)
@@ -863,6 +863,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return _M_data()[__n];
       }
 
+      /**
+       *  @brief  Provides access to the data contained in the %string.
+       *  @param __n The index of the character to access.
+       *  @return  Read/write reference to the character.
+       *  @throw  std::out_of_range  If @a n is an invalid index.
+       *
+       *  This function provides for safer data access.  The parameter is
+       *  first checked that it is in the range of the string.  The function
+       *  throws out_of_range if the check fails.  Success results in
+       *  unsharing the string.
+       */
+      reference
+      at(size_type __n)
+      {
+	if (__n >= size())
+	  __throw_out_of_range(__N("basic_string::at"));
+	_M_leak();
+	return _M_data()[__n];
+      }
+
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
       /**
        *  Returns a read/write reference to the data at the first
@@ -897,26 +917,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { return operator[](this->size() - 1); }
 #endif
 
-      /**
-       *  @brief  Provides access to the data contained in the %string.
-       *  @param __n The index of the character to access.
-       *  @return  Read/write reference to the character.
-       *  @throw  std::out_of_range  If @a n is an invalid index.
-       *
-       *  This function provides for safer data access.  The parameter is
-       *  first checked that it is in the range of the string.  The function
-       *  throws out_of_range if the check fails.  Success results in
-       *  unsharing the string.
-       */
-      reference
-      at(size_type __n)
-      {
-	if (__n >= size())
-	  __throw_out_of_range(__N("basic_string::at"));
-	_M_leak();
-	return _M_data()[__n];
-      }
-
       // Modifiers:
       /**
        *  @brief  Append a string to this string.
@@ -1392,6 +1392,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       iterator
       erase(iterator __first, iterator __last);
  
+#ifdef __GXX_EXPERIMENTAL_CXX0X__
+      /**
+       *  @brief  Remove the last character.
+       *
+       *  The string must be non-empty.
+       */
+      void
+      pop_back()
+      { erase(size()-1, 1); }
+#endif // __GXX_EXPERIMENTAL_CXX0X__
+
       /**
        *  @brief  Replace characters with value from another string.
        *  @param __pos  Index of first character to replace.
Index: include/debug/string
===================================================================
--- include/debug/string	(revision 179472)
+++ include/debug/string	(working copy)
@@ -580,6 +580,16 @@ namespace __gnu_debug
       return iterator(__res, this);
     }
 
+#ifdef __GXX_EXPERIMENTAL_CXX0X__
+    void
+    pop_back()
+    {
+      __glibcxx_check_nonempty();
+      _Base::pop_back();
+      this->_M_invalidate_all();
+    }
+#endif // __GXX_EXPERIMENTAL_CXX0X__
+
     basic_string&
     replace(size_type __pos1, size_type __n1, const basic_string& __str)
     {
Index: include/ext/vstring.h
===================================================================
--- include/ext/vstring.h	(revision 179472)
+++ include/ext/vstring.h	(working copy)
@@ -1137,6 +1137,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return iterator(this->_M_data() + __pos);
       }
 
+#ifdef __GXX_EXPERIMENTAL_CXX0X__
+      /**
+       *  @brief  Remove the last character.
+       *
+       *  The string must be non-empty.
+       */
+      void
+      pop_back()
+      { this->_M_erase(size()-1, 1); }
+#endif // __GXX_EXPERIMENTAL_CXX0X__
+
       /**
        *  @brief  Replace characters with value from another string.
        *  @param __pos  Index of first character to replace.
Index: testsuite/21_strings/basic_string/pop_back.cc
===================================================================
--- testsuite/21_strings/basic_string/pop_back.cc	(revision 0)
+++ testsuite/21_strings/basic_string/pop_back.cc	(revision 0)
@@ -0,0 +1,41 @@
+// Copyright (C) 2011 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// 21.4.6.5 basic_string::pop_back
+// { dg-options "-std=gnu++0x" }
+
+#include <string>
+#include <testsuite_hooks.h>
+
+void test01()
+{
+  bool test __attribute__((unused)) = true;
+
+  const std::string cstr("Badger");
+  std::string str = cstr;
+  str.pop_back();
+  VERIFY( str.size() == cstr.size() - 1 );
+
+  str += cstr.back();
+  VERIFY( str == cstr );
+}
+
+int main()
+{ 
+  test01();
+  return 0;
+}
Index: testsuite/ext/vstring/pop_back.cc
===================================================================
--- testsuite/ext/vstring/pop_back.cc	(revision 0)
+++ testsuite/ext/vstring/pop_back.cc	(revision 0)
@@ -0,0 +1,45 @@
+// Copyright (C) 2011 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// 21.4.6.5 basic_string::pop_back
+// { dg-options "-std=gnu++0x" }
+
+#include <ext/vstring.h>
+#include <testsuite_hooks.h>
+
+template<typename StrT>
+int test01()
+{
+  bool test __attribute__((unused)) = true;
+
+  const StrT cstr("Badger");
+  StrT str = cstr;
+  str.pop_back();
+  VERIFY( str.size() == cstr.size() - 1 );
+
+  str += cstr.back();
+  VERIFY( str == cstr );
+
+  return test;
+}
+
+int main()
+{ 
+  test01<__gnu_cxx::__sso_string>();
+  test01<__gnu_cxx::__rc_string>();
+  return 0;
+}
