diff --git a/lib/ArgVerifier.js b/lib/ArgVerifier.js
index e181954..8856fe2 100644
--- a/lib/ArgVerifier.js
+++ b/lib/ArgVerifier.js
@@ -3,9 +3,12 @@ var topiarist = require('topiarist');
 
 function verifierMethod(verifier, methodName) {
   return function() {
-    if(this.argValue === undefined) throw new ArgumentError(this.argName + ' argument must be provided.');
+    if(!this.skipVerification) {
+      if(this.argValue === undefined) throw new ArgumentError(this.argName + ' argument must be provided.');
+
+      verifier[methodName].apply(this, arguments);
+    }
 
-    verifier[methodName].apply(this, arguments);
     return this.argsVerifier;
   };
 }
@@ -22,4 +25,14 @@ ArgVerifier.addVerifier = function(verifier) {
   }
 };
 
+Object.defineProperty(ArgVerifier.prototype, 'optionally', {
+  get: function optionally() {
+    if((this.argValue === undefined) || (this.argValue === null)) {
+      this.skipVerification = true;
+    }
+
+    return this;
+  }
+});
+
 module.exports = ArgVerifier;
diff --git a/package.json b/package.json
index 5bffdbb..676cc12 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "typester",
-	"version": "0.1.1",
+	"version": "0.2.0",
 	"description": "Fluent type verification for JavaScript",
 	"main": "lib/typester.js",
 	"dependencies": {
diff --git a/spec/test/typester.js b/spec/test/typester.js
index c1f1612..d579833 100644
--- a/spec/test/typester.js
+++ b/spec/test/typester.js
@@ -5,41 +5,63 @@ var ArgumentError = typester.ArgumentError;
 describe('typester', function() {
 	it('throws an ArgumentError if we try to validate a non-existent argument', function() {
     function func() {
-      using([])
+      using(arguments)
         .verify('num').isA(Number);
     }
 
     func.should.throw('num argument must be provided');
     func.should.throw(ArgumentError);
+		func.bind(func, 10).should.not.throw();
 	});
 
-	it('works with real function argument arrays', function() {
+	it('throws an ArgumentError if we try to validate a subsequent non-existent argument', function() {
 		function func() {
 			using(arguments)
+				.verify('bool').isA(Boolean)
 				.verify('num').isA(Number);
 		}
 
-		func.bind(func, undefined).should.throw(ArgumentError);
-		func.bind(func, 10).should.not.throw();
+		func.bind(func, true).should.throw('num argument must be provided');
+		func.bind(func, true).should.throw(ArgumentError);
+		func.bind(func, true, 10).should.not.throw();
 	});
 
-	it('throws an ArgumentError if we try to validate a subsequent non-existent argument', function() {
+	it('throws a TypeError if we try to validate a provided argument is of the wrong type', function() {
 		function func() {
 			using([true])
-				.verify('bool').isA(Boolean)
 				.verify('num').isA(Number);
 		}
 
-		func.should.throw('num argument must be provided');
-		func.should.throw(ArgumentError);
+		func.should.throw(TypeError);
+		func.should.throw('num argument must be a Number');
 	});
 
-	it('throws a TypeError if we try to validate a provided argument is of the wrong type', function() {
+	it('does not require optional arguments to be provided, but throws if they are incorrect', function() {
 		function func() {
-			using([true])
-				.verify('num').isA(Number);
+			using(arguments)
+				.verify('bool').isA(Boolean)
+				.verify('num').optionally.isA(Number);
 		}
 
-		func.should.throw(TypeError);
+		func.bind(func, true).should.not.throw();
+		func.bind(func, true, 10).should.not.throw();
+		func.bind(func, true, '10').should.throw(TypeError);
+		func.bind(func, true, '').should.throw(TypeError);
+		func.bind(func, true, []).should.throw(TypeError);
+	});
+
+	it('allows mandatory arguments to appear after an optional argument', function() {
+		function func() {
+			using(arguments)
+				.verify('num').optionally.isA(Number)
+				.verify('bool').isA(Boolean);
+		}
+
+		func.bind(func, null, true).should.not.throw();
+		func.bind(func, undefined, true).should.not.throw();
+		func.bind(func, null).should.throw(ArgumentError);
+		func.bind(func, null, {}).should.throw(TypeError);
+		func.bind(func, '10', true).should.throw(TypeError);
+		func.bind(func, '10', true).should.throw('num argument must be a Number');
 	});
 });