diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index ab391639d0..e3cd0da60d 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -90,10 +90,12 @@ namespace ts {
         let lastContainer: Node;
         let symbolCount = 0;
         let Symbol = objectAllocator.getSymbolConstructor();
+        let classifiableNames: Map<string> = {}; 
 
         if (!file.locals) {
             bind(file);
             file.symbolCount = symbolCount;
+            file.classifiableNames = classifiableNames;
         }
 
         return;
@@ -194,6 +196,11 @@ namespace ts {
                 symbol = hasProperty(symbolTable, name)
                     ? symbolTable[name]
                     : (symbolTable[name] = createSymbol(SymbolFlags.None, name));
+                
+                if (name && (includes & SymbolFlags.Classifiable)) {
+                    classifiableNames[name] = name;   
+                } 
+
                 if (symbol.flags & excludes) {
                     if (node.name) {
                         node.name.parent = node;
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index aa8a413aaa..8ab3e73858 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -148,6 +148,7 @@ namespace ts {
         let commonSourceDirectory: string;
         let diagnosticsProducingTypeChecker: TypeChecker;
         let noDiagnosticsTypeChecker: TypeChecker;
+        let classifiableNames: Map<string>;
 
         let start = new Date().getTime();
 
@@ -172,6 +173,7 @@ namespace ts {
             getDeclarationDiagnostics,
             getCompilerOptionsDiagnostics,
             getTypeChecker,
+            getClassifiableNames,
             getDiagnosticsProducingTypeChecker,
             getCommonSourceDirectory: () => commonSourceDirectory,
             emit,
@@ -183,6 +185,20 @@ namespace ts {
         };
         return program;
 
+        function getClassifiableNames() {
+            if (!classifiableNames) {
+                // Initialize a checker so that all our files are bound.
+                getTypeChecker();
+                classifiableNames = {};
+
+                for (let sourceFile of files) {
+                    copyMap(sourceFile.classifiableNames, classifiableNames);
+                }
+            }
+
+            return classifiableNames;
+        }
+
         function getEmitHost(writeFileCallback?: WriteFileCallback): EmitHost {
             return {
                 getCanonicalFileName: fileName => host.getCanonicalFileName(fileName),
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index cf7a6dff2d..8be7c1792a 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -1172,6 +1172,8 @@ namespace ts {
         // Stores a line map for the file.
         // This field should never be used directly to obtain line map, use getLineMap function instead.
         /* @internal */ lineMap: number[];
+
+        /* @internal */ classifiableNames?: Map<string>;
     }
 
     export interface ScriptReferenceHost {
@@ -1223,6 +1225,8 @@ namespace ts {
         // language service).
         /* @internal */ getDiagnosticsProducingTypeChecker(): TypeChecker;
 
+        /* @internal */ getClassifiableNames(): Map<string>;
+
         /* @internal */ getNodeCount(): number;
         /* @internal */ getIdentifierCount(): number;
         /* @internal */ getSymbolCount(): number;
@@ -1519,6 +1523,11 @@ namespace ts {
 
         PropertyOrAccessor = Property | Accessor,
         Export = ExportNamespace | ExportType | ExportValue,
+
+        /* @internal */
+        // The set of things we consider semantically classifiable.  Used to speed up the LS during 
+        // classification.
+        Classifiable = Class | Enum | TypeAlias | Interface | TypeParameter | Module,
     }
 
     export interface Symbol {
diff --git a/src/services/services.ts b/src/services/services.ts
index 105859f7cc..3939e62cfd 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -5992,6 +5992,7 @@ namespace ts {
             let typeChecker = program.getTypeChecker();
 
             let result: number[] = [];
+            let classifiableNames = program.getClassifiableNames();
             processNode(sourceFile);
 
             return { spans: result, endOfLineState: EndOfLineState.None };
@@ -6004,6 +6005,9 @@ namespace ts {
 
             function classifySymbol(symbol: Symbol, meaningAtPosition: SemanticMeaning): ClassificationType {
                 let flags = symbol.getFlags();
+                if ((flags & SymbolFlags.Classifiable) === SymbolFlags.None) {
+                    return;
+                }
 
                 if (flags & SymbolFlags.Class) {
                     return ClassificationType.className;
@@ -6048,11 +6052,18 @@ namespace ts {
                 // Only walk into nodes that intersect the requested span.
                 if (node && textSpanIntersectsWith(span, node.getFullStart(), node.getFullWidth())) {
                     if (node.kind === SyntaxKind.Identifier && !nodeIsMissing(node)) {
-                        let symbol = typeChecker.getSymbolAtLocation(node);
-                        if (symbol) {
-                            let type = classifySymbol(symbol, getMeaningFromLocation(node));
-                            if (type) {
-                                pushClassification(node.getStart(), node.getWidth(), type);
+                        let identifier = <Identifier>node;
+
+                        // Only bother calling into the typechecker if this is an identifier that
+                        // could possibly resolve to a type name.  This makes classification run
+                        // in a third of the time it would normally take.
+                        if (classifiableNames[identifier.text]) {
+                            let symbol = typeChecker.getSymbolAtLocation(node);
+                            if (symbol) {
+                                let type = classifySymbol(symbol, getMeaningFromLocation(node));
+                                if (type) {
+                                    pushClassification(node.getStart(), node.getWidth(), type);
+                                }
                             }
                         }
                     }