diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index c1011e57568..0a2df4f70d5 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -3099,6 +3099,7 @@ namespace ts {
             case SyntaxKind.ThisType:
             case SyntaxKind.TypeOperator:
             case SyntaxKind.IndexedAccessType:
+            case SyntaxKind.MappedType:
             case SyntaxKind.LiteralType:
                 // Types and signatures are TypeScript syntax, and exclude all other facts.
                 transformFlags = TransformFlags.AssertTypeScript;
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index cf0c048ecbf..647bc7e3e5d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -6002,6 +6002,8 @@ namespace ts {
                     return getTypeFromTypeOperatorNode(<TypeOperatorNode>node);
                 case SyntaxKind.IndexedAccessType:
                     return getTypeFromIndexedAccessTypeNode(<IndexedAccessTypeNode>node);
+                case SyntaxKind.MappedType:
+                    return unknownType;  // !!!
                 // This function assumes that an identifier or qualified name is a type expression
                 // Callers should first ensure this by calling isTypeNode
                 case SyntaxKind.Identifier:
@@ -15072,6 +15074,10 @@ namespace ts {
             getTypeFromIndexedAccessTypeNode(node);
         }
 
+        function checkMappedType(node: MappedTypeNode) {
+            node; // !!!
+        }
+
         function isPrivateWithinAmbient(node: Node): boolean {
             return (getModifierFlags(node) & ModifierFlags.Private) && isInAmbientContext(node);
         }
@@ -18312,6 +18318,8 @@ namespace ts {
                     return checkSourceElement((<ParenthesizedTypeNode | TypeOperatorNode>node).type);
                 case SyntaxKind.IndexedAccessType:
                     return checkIndexedAccessType(<IndexedAccessTypeNode>node);
+                case SyntaxKind.IndexedAccessType:
+                    return checkMappedType(<MappedTypeNode>node);
                 case SyntaxKind.FunctionDeclaration:
                     return checkFunctionDeclaration(<FunctionDeclaration>node);
                 case SyntaxKind.Block:
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 92a3dcbef11..f4a41d8da12 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -139,6 +139,10 @@ namespace ts {
             case SyntaxKind.IndexedAccessType:
                 return visitNode(cbNode, (<IndexedAccessTypeNode>node).objectType) ||
                     visitNode(cbNode, (<IndexedAccessTypeNode>node).indexType);
+            case SyntaxKind.MappedType:
+                return visitNode(cbNode, (<MappedTypeNode>node).iterationTypeName) ||
+                    visitNode(cbNode, (<MappedTypeNode>node).indexType) ||
+                    visitNode(cbNode, (<MappedTypeNode>node).type);
             case SyntaxKind.LiteralType:
                 return visitNode(cbNode, (<LiteralTypeNode>node).literal);
             case SyntaxKind.ObjectBindingPattern:
@@ -2399,6 +2403,30 @@ namespace ts {
             return members;
         }
 
+        function isStartOfMappedType() {
+            nextToken();
+            if (token() === SyntaxKind.ReadonlyKeyword) {
+                nextToken();
+            }
+            return token() === SyntaxKind.OpenBracketToken && nextTokenIsIdentifier() && nextToken() === SyntaxKind.InKeyword;
+        }
+
+        function parseMappedType() {
+            const node = <MappedTypeNode>createNode(SyntaxKind.MappedType);
+            parseExpected(SyntaxKind.OpenBraceToken);
+            node.readonlyToken = parseOptionalToken(SyntaxKind.ReadonlyKeyword);
+            parseExpected(SyntaxKind.OpenBracketToken);
+            node.iterationTypeName = parseIdentifier();
+            parseExpected(SyntaxKind.InKeyword);
+            node.indexType = parseType();
+            parseExpected(SyntaxKind.CloseBracketToken);
+            node.questionToken = parseOptionalToken(SyntaxKind.QuestionToken);
+            node.type = parseTypeAnnotation();
+            parseSemicolon();
+            parseExpected(SyntaxKind.CloseBraceToken);
+            return finishNode(node);
+        }
+
         function parseTupleType(): TupleTypeNode {
             const node = <TupleTypeNode>createNode(SyntaxKind.TupleType);
             node.elementTypes = parseBracketedList(ParsingContext.TupleElementTypes, parseType, SyntaxKind.OpenBracketToken, SyntaxKind.CloseBracketToken);
@@ -2472,7 +2500,7 @@ namespace ts {
                 case SyntaxKind.TypeOfKeyword:
                     return parseTypeQuery();
                 case SyntaxKind.OpenBraceToken:
-                    return parseTypeLiteral();
+                    return lookAhead(isStartOfMappedType) ? parseMappedType() : parseTypeLiteral();
                 case SyntaxKind.OpenBracketToken:
                     return parseTupleType();
                 case SyntaxKind.OpenParenToken:
diff --git a/src/compiler/transformers/ts.ts b/src/compiler/transformers/ts.ts
index 1362746ba57..65e31ab1ee6 100644
--- a/src/compiler/transformers/ts.ts
+++ b/src/compiler/transformers/ts.ts
@@ -302,6 +302,7 @@ namespace ts {
                 case SyntaxKind.ThisType:
                 case SyntaxKind.TypeOperator:
                 case SyntaxKind.IndexedAccessType:
+                case SyntaxKind.MappedType:
                 case SyntaxKind.LiteralType:
                     // TypeScript type nodes are elided.
 
@@ -1787,6 +1788,7 @@ namespace ts {
                 case SyntaxKind.TypeQuery:
                 case SyntaxKind.TypeOperator:
                 case SyntaxKind.IndexedAccessType:
+                case SyntaxKind.MappedType:
                 case SyntaxKind.TypeLiteral:
                 case SyntaxKind.AnyKeyword:
                 case SyntaxKind.ThisType:
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 381289b133b..22fbe29c76b 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -219,6 +219,7 @@ namespace ts {
         ThisType,
         TypeOperator,
         IndexedAccessType,
+        MappedType,
         LiteralType,
         // Binding patterns
         ObjectBindingPattern,
@@ -519,6 +520,7 @@ namespace ts {
     export type EqualsGreaterThanToken = Token<SyntaxKind.EqualsGreaterThanToken>;
     export type EndOfFileToken = Token<SyntaxKind.EndOfFileToken>;
     export type AtToken = Token<SyntaxKind.AtToken>;
+    export type ReadonlyToken = Token<SyntaxKind.ReadonlyKeyword>;
 
     export type Modifier
         = Token<SyntaxKind.AbstractKeyword>
@@ -897,6 +899,15 @@ namespace ts {
         indexType: TypeNode;
     }
 
+    export interface MappedTypeNode extends TypeNode {
+        kind: SyntaxKind.MappedType;
+        readonlyToken?: ReadonlyToken;
+        iterationTypeName: Identifier;
+        indexType: TypeNode;
+        questionToken?: QuestionToken;
+        type?: TypeNode;
+    }
+
     export interface LiteralTypeNode extends TypeNode {
         kind: SyntaxKind.LiteralType;
         literal: Expression;