diff --git a/lib/mujs/index.ts b/lib/mujs/index.ts
index d372dca13..86feba02c 100644
--- a/lib/mujs/index.ts
+++ b/lib/mujs/index.ts
@@ -1,5 +1,6 @@
 // Copyright 2016 Marapongo, Inc. All rights reserved.
 
 import * as lib from "./lib";
-export { lib };
+import * as runtime from "./runtime";
+export { lib, runtime };
 
diff --git a/lib/mujs/lib/error.ts b/lib/mujs/lib/errors.ts
similarity index 85%
rename from lib/mujs/lib/error.ts
rename to lib/mujs/lib/errors.ts
index 4ce766746..b15285734 100644
--- a/lib/mujs/lib/error.ts
+++ b/lib/mujs/lib/errors.ts
@@ -15,3 +15,10 @@ export class Error {
 //     SyntaxError, TypeError, etc.)  Unfortunately, unless we come up with some clever way of mapping MuIL runtime
 //     errors into their ECMAScript equivalents, we aren't going to have perfect compatibility with error path logic.
 
+export class TypeError extends Error {
+    constructor(message?: string) {
+        super(message);
+        this.name = "TypeError";
+    }
+}
+
diff --git a/lib/mujs/lib/index.ts b/lib/mujs/lib/index.ts
index 02ce89b91..b15d056a4 100644
--- a/lib/mujs/lib/index.ts
+++ b/lib/mujs/lib/index.ts
@@ -2,5 +2,6 @@
 
 // The lib module exports the standard ECMAScript APIs.
 
-export * from "./error";
+export * from "./errors";
+export * from "./types";
 
diff --git a/lib/mujs/lib/types.ts b/lib/mujs/lib/types.ts
new file mode 100644
index 000000000..ac4ff57d7
--- /dev/null
+++ b/lib/mujs/lib/types.ts
@@ -0,0 +1,23 @@
+// Copyright 2016 Marapongo, Inc. All rights reserved.
+
+export class Boolean {
+    public data: boolean;
+    constructor(data: boolean) {
+        this.data = data;
+    }
+}
+
+export class String {
+    public data: string;
+    constructor(data: string) {
+        this.data = data;
+    }
+}
+
+export class Number {
+    public data: number;
+    constructor(data: number) {
+        this.data = data;
+    }
+}
+
diff --git a/lib/mujs/runtime/assert.ts b/lib/mujs/runtime/assert.ts
new file mode 100644
index 000000000..ae9b7c6ac
--- /dev/null
+++ b/lib/mujs/runtime/assert.ts
@@ -0,0 +1,10 @@
+// Copyright 2016 Marapongo, Inc. All rights reserved.
+
+import {Error} from "../lib";
+
+export function assert(b: boolean): void {
+    if (!b) {
+        throw new Error("An assertion has failed");
+    }
+}
+
diff --git a/lib/mujs/runtime/ecmascript.ts b/lib/mujs/runtime/ecmascript.ts
new file mode 100644
index 000000000..fff1e3399
--- /dev/null
+++ b/lib/mujs/runtime/ecmascript.ts
@@ -0,0 +1,216 @@
+// Copyright 2016 Marapongo, Inc. All rights reserved.
+
+import * as mu from "@mu/mu";
+import {assert} from "./assert";
+import {Boolean, Number, String, TypeError} from "../lib";
+
+// The abstract operation ToString converts argument to a value of type String according to the table in
+// https://tc39.github.io/ecma262/#sec-tostring.
+export function toString(argument: Object): string {
+    if (argument === undefined) {
+        return "undefined";
+    }
+    if (argument === null) {
+        return "null";
+    }
+    if (isBoolean(argument)) {
+        if (argument === true) {
+            return "true";
+        }
+        return "false";
+    }
+    if (isNumber(argument)) {
+    }
+    if (isSymbol(argument)) {
+        throw new TypeError();
+    }
+    if (isString(argument)) {
+        return <string>argument;
+    }
+
+    // For other objects, convert to a primitive value and stringify that.
+    let primValue: Object = toPrimitive(argument, "string");
+    return toString(primValue);
+}
+
+export function isObject(input: Object): boolean {
+    return !isPrimitive(input);
+}
+
+export function isPrimitive(input: Object): boolean {
+    return input === undefined || input === null ||
+            isBoolean(input) || isNumber(input) || isString(input) || isSymbol(input)
+}
+
+export function isBoolean(input: Object): boolean {
+    return (typeof(input) === "bool");
+}
+
+export function isNumber(input: Object): boolean {
+    return (typeof(input) === "number");
+}
+
+export function isString(input: Object): boolean {
+    return (typeof(input) === "string");
+}
+
+export function isSymbol(input: Object): boolean {
+    // TODO: implement symbols.
+    return false;
+}
+
+// The abstract operation toPrimitive takes an input argument and an optional argument preferredType.  The abstract
+// operation toPrimitive converts its input argument to a non-Object type.  If an object is capable of converting to
+// more than one primitive type, it may use the optional hint preferredType to favor that type.  Conversion occurs
+// according to the table in https://tc39.github.io/ecma262/#sec-toprimitive.
+export function toPrimitive(input: Object, preferredType: string): Object {
+    if (isPrimitive(input)) {
+        return input;
+    }
+
+    let hint: string;
+    if (preferredType) {
+        hint = preferredType;
+    }
+    else {
+        hint = "default";
+    }
+
+    let exoticToPrim: Object | undefined = getMethod(input, "@@toPrimitive");
+    if (exoticToPrim) {
+        let result: Object = call(exoticToPrim, input, [ hint ]);
+        if (isObject(result)) {
+            throw new TypeError("");
+        }
+        return result;
+    }
+
+    if (hint === "default") {
+        hint = "number";
+    }
+    return ordinaryToPrimitive(input, hint);
+}
+
+// When the abstract operation OrdinaryToPrimitive is called with arguments O and hint, the steps outlined in
+// https://tc39.github.io/ecma262/#sec-ordinarytoprimitive are taken.
+export function ordinaryToPrimitive(o: Object, hint: string): Object {
+    assert(isObject(o));
+
+    let methodNames: string[];
+    switch (hint) {
+        case "string":
+            methodNames = [ "toString", "valueOf" ];
+            break;
+        case "number":
+            methodNames = [ "valueOf", "toString" ];
+            break;
+        default:
+            assert(false);
+            methodNames = [];
+    }
+
+    for (let name of methodNames) {
+        let method: Object = get(o, name);
+        if (isCallable(method)) {
+            let result: Object = call(method, o);
+            if (isPrimitive(result)) {
+                return result;
+            }
+        }
+    }
+
+    throw new TypeError();
+}
+
+// The abstract operation ToObject converts argument to a value of type Object according to the table in
+// https://tc39.github.io/ecma262/#sec-toobject.
+export function toObject(argument: Object): Object {
+    if (argument === undefined || argument === null) {
+        throw new TypeError();
+    }
+    if (isBoolean(argument)) {
+        return new Boolean(<boolean>argument);
+    }
+    if (isNumber(argument)) {
+        return new Number(<number>argument);
+    }
+    if (isString(argument)) {
+        return new String(<string>argument);
+    }
+    if (isSymbol(argument)) {
+        // TODO: implement symbols.
+    }
+    return argument;
+}
+
+// The abstract operation Get is used to retrieve the value of a specific property of an object. The operation is called
+// with arguments O and P where O is the object and P is the property key. This abstract operation performs the steps
+// outlined in https://tc39.github.io/ecma262/#sec-get-o-p.
+export function get(o: Object, p: string): Object {
+    assert(isObject(o));
+    assert(isPropertyKey(p));
+    return (<any>o)[<any>p];
+}
+
+// The abstract operation GetV is used to retrieve the value of a specific property of an ECMAScript language value. If
+// the value is not an object, the property lookup is performed using a wrapper object appropriate for the type of the
+// value. The operation is called with arguments V and P where V is the value and P is the property key. This abstract
+// operation performs the steps outlined in https://tc39.github.io/ecma262/#sec-getv.
+export function getV(v: Object, p: Object): Object {
+    assert(isPropertyKey(p));
+    let o: Object = toObject(v);
+    return (<any>o)[<any>p];
+}
+
+// The abstract operation GetMethod is used to get the value of a specific property of an ECMAScript language value when
+// the value of the property is expected to be a function. The operation is called with arguments V and P where V is the
+// ECMAScript language value, P is the property key. This abstract operation performs the steps outlined in
+// https://tc39.github.io/ecma262/#sec-getmethod.
+export function getMethod(v: Object, p: Object): Object | undefined {
+    assert(isPropertyKey(p));
+    let func: Object = getV(v, p);
+    if (func === undefined || func === null) {
+        return undefined;
+    }
+    if (!isCallable(func)) {
+        throw new TypeError();
+    }
+    return func;
+}
+
+// The abstract operation IsPropertyKey determines if argument, which must be an ECMAScript language value, is a value
+// that may be used as a property key, as described in https://tc39.github.io/ecma262/#sec-ispropertykey.
+export function isPropertyKey(argument: Object): boolean {
+    if (isString(argument)) {
+        return true;
+    }
+    if (isSymbol(argument)) {
+        return true;
+    }
+    return false;
+}
+
+// The abstract operation Call is used to call the [[Call]] internal method of a function object. The operation is
+// called with arguments F, V, and optionally argumentsList where F is the function object, V is an ECMAScript language
+// value that is the this value of the [[Call]], and argumentsList is the value passed to the corresponding argument of
+// the internal method. If argumentsList is not present, a new empty List is used as its value. This abstract operation
+// performs the steps outlined in https://tc39.github.io/ecma262/#sec-call.
+export function call(f: Object, v: Object, argumentsList?: Object[]): Object {
+    if (!isCallable(f)) {
+        throw new TypeError();
+    }
+    if (!argumentsList) {
+        argumentsList = [];
+    }
+    return mu.runtime.dynamicInvoke(f, v, argumentsList);
+}
+
+// The abstract operation IsCallable determines if argument, which must be an ECMAScript language value, is a callable
+// function with a [[Call]] internal method, as per https://tc39.github.io/ecma262/#sec-iscallable.
+export function isCallable(argument: Object): boolean {
+    if (!isObject(argument)) {
+        return false;
+    }
+    return mu.runtime.isFunction(argument);
+}
+
diff --git a/lib/mujs/runtime/index.ts b/lib/mujs/runtime/index.ts
new file mode 100644
index 000000000..152b8535f
--- /dev/null
+++ b/lib/mujs/runtime/index.ts
@@ -0,0 +1,7 @@
+// Copyright 2016 Marapongo, Inc. All rights reserved.
+
+// The runtime module contains helpers that the MuJS compiler emits to do certain things.
+
+export * from "./assert";
+export * from "./ecmascript";
+
diff --git a/lib/mujs/tsconfig.json b/lib/mujs/tsconfig.json
index 5aeaf0008..9d48666c8 100644
--- a/lib/mujs/tsconfig.json
+++ b/lib/mujs/tsconfig.json
@@ -19,7 +19,10 @@
         "index.ts",
 
         "lib/index.ts",
-        "lib/error.ts"
+        "lib/errors.ts",
+        "lib/types.ts",
+
+        "runtime/ecmascript"
     ]
 }