diff --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
index 2d35b4d99034..aa01b7fdf06f 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -192,6 +192,7 @@ public:
   QualType VoidPtrTy, NullPtrTy;
   QualType OverloadTy;
   QualType DependentTy;
+  QualType UndeducedAutoTy;
 
   ASTContext(const LangOptions& LOpts, SourceManager &SM, TargetInfo &t,
              IdentifierTable &idents, SelectorTable &sels,
diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
index 225a42382187..321b1f204fcf 100644
--- a/clang/include/clang/AST/Type.h
+++ b/clang/include/clang/AST/Type.h
@@ -572,7 +572,10 @@ public:
     NullPtr,  // This is the type of C++0x 'nullptr'.
 
     Overload,  // This represents the type of an overloaded function declaration.
-    Dependent  // This represents the type of a type-dependent expression.
+    Dependent, // This represents the type of a type-dependent expression.
+    
+    UndeducedAuto  // In C++0x, this represents the type of an auto variable
+                   // that has not been deduced yet.
   };
 private:
   Kind TypeKind;
diff --git a/clang/include/clang/Parse/DeclSpec.h b/clang/include/clang/Parse/DeclSpec.h
index 10c5ee39ec50..300602e5147c 100644
--- a/clang/include/clang/Parse/DeclSpec.h
+++ b/clang/include/clang/Parse/DeclSpec.h
@@ -83,6 +83,7 @@ public:
     TST_typeofType,
     TST_typeofExpr,
     TST_decltype,     // C++0x decltype
+    TST_auto,         // C++0x auto
     TST_error         // erroneous type
   };
   
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 16a62fdd8cdd..12f75ae863a2 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -179,6 +179,10 @@ void ASTContext::InitBuiltinTypes() {
   // expressions.
   InitBuiltinType(DependentTy,         BuiltinType::Dependent);
 
+  // Placeholder type for C++0x auto declarations whose real type has 
+  // not yet been deduced.
+  InitBuiltinType(UndeducedAutoTy, BuiltinType::UndeducedAuto);
+  
   // C99 6.2.5p11.
   FloatComplexTy      = getComplexType(FloatTy);
   DoubleComplexTy     = getComplexType(DoubleTy);
diff --git a/clang/lib/CodeGen/Mangle.cpp b/clang/lib/CodeGen/Mangle.cpp
index 24e441a29635..b5ad5acc0162 100644
--- a/clang/lib/CodeGen/Mangle.cpp
+++ b/clang/lib/CodeGen/Mangle.cpp
@@ -539,6 +539,9 @@ void CXXNameMangler::mangleType(const BuiltinType *T) {
     assert(false && 
            "Overloaded and dependent types shouldn't get to name mangling");
     break;
+  case BuiltinType::UndeducedAuto:
+    assert(0 && "Should not see undeduced auto here");
+    break;
   }
 }
 
diff --git a/clang/lib/Frontend/PCHWriter.cpp b/clang/lib/Frontend/PCHWriter.cpp
index 808df70df30d..e93219e01d5c 100644
--- a/clang/lib/Frontend/PCHWriter.cpp
+++ b/clang/lib/Frontend/PCHWriter.cpp
@@ -1909,6 +1909,9 @@ void PCHWriter::AddTypeRef(QualType T, RecordData &Record) {
     case BuiltinType::NullPtr:    ID = pch::PREDEF_TYPE_NULLPTR_ID;    break;
     case BuiltinType::Overload:   ID = pch::PREDEF_TYPE_OVERLOAD_ID;   break;
     case BuiltinType::Dependent:  ID = pch::PREDEF_TYPE_DEPENDENT_ID;  break;
+    case BuiltinType::UndeducedAuto:
+      assert(0 && "Should not see undeduced auto here");
+      break;
     }
 
     Record.push_back((ID << 3) | T.getCVRQualifiers());
diff --git a/clang/lib/Parse/DeclSpec.cpp b/clang/lib/Parse/DeclSpec.cpp
index d8c6986f9ea6..8b3b2851c1e0 100644
--- a/clang/lib/Parse/DeclSpec.cpp
+++ b/clang/lib/Parse/DeclSpec.cpp
@@ -173,6 +173,7 @@ const char *DeclSpec::getSpecifierName(DeclSpec::TST T) {
   case DeclSpec::TST_typename:    return "type-name";
   case DeclSpec::TST_typeofType:
   case DeclSpec::TST_typeofExpr:  return "typeof";
+  case DeclSpec::TST_auto:       return "auto";
   }
 }
 
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index c11383c3eca9..b2b2f31dd6ea 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -926,7 +926,10 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
       isInvalid = DS.SetStorageClassSpec(DeclSpec::SCS_static, Loc, PrevSpec);
       break;
     case tok::kw_auto:
-      isInvalid = DS.SetStorageClassSpec(DeclSpec::SCS_auto, Loc, PrevSpec);
+      if (getLang().CPlusPlus0x)
+        isInvalid = DS.SetTypeSpecType(DeclSpec::TST_auto, Loc, PrevSpec);
+      else
+        isInvalid = DS.SetStorageClassSpec(DeclSpec::SCS_auto, Loc, PrevSpec);
       break;
     case tok::kw_register:
       isInvalid = DS.SetStorageClassSpec(DeclSpec::SCS_register, Loc, PrevSpec);
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 8a0ad089b68f..b58414234438 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -245,6 +245,11 @@ QualType Sema::ConvertDeclSpecToType(const DeclSpec &DS,
     Result = Context.getDecltypeType(E);
     break;
   }
+  case DeclSpec::TST_auto: {
+    // TypeQuals handled by caller.
+    Result = Context.UndeducedAutoTy;
+    break;
+  }
     
   case DeclSpec::TST_error:
     Result = Context.IntTy;
diff --git a/clang/test/SemaCXX/auto-cxx0x.cpp b/clang/test/SemaCXX/auto-cxx0x.cpp
new file mode 100644
index 000000000000..33156ef23d2e
--- /dev/null
+++ b/clang/test/SemaCXX/auto-cxx0x.cpp
@@ -0,0 +1,5 @@
+// RUN: clang-cc -fsyntax-only -verify %s -std=c++0x
+void f() {
+  auto int a; // expected-error{{cannot combine with previous 'auto' declaration specifier}}
+  int auto b; // expected-error{{cannot combine with previous 'int' declaration specifier}}
+}
diff --git a/clang/test/SemaCXX/auto-cxx98.cpp b/clang/test/SemaCXX/auto-cxx98.cpp
new file mode 100644
index 000000000000..14670cd69942
--- /dev/null
+++ b/clang/test/SemaCXX/auto-cxx98.cpp
@@ -0,0 +1,5 @@
+// RUN: clang-cc -fsyntax-only -verify %s -std=c++98
+void f() {
+  auto int a;
+  int auto b;
+}