http://blogs.msdn.com/b/hongmeig1/archive/2012/02/27/supporting-multiple-authentication-schemes-with-web-api.aspxWith the newly released Web API Beta bits ( http://www.asp.net/web-api) , you can support multiple authentication from client. Say you want the client send both the username/password as well as Client Certificate for SSL. For the web hosted scenarioen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)