Just created custom WCF service in SharePoint 2010. Incredibly straightforward which is just brilliant. 1. Followed this article on msdn 2. I also needed to add the following attributes to the service class [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] [BasicHttpBindingServiceMetadataExchangeEndpoint] From here on it works and can be referenced (“Add Service reference” in Visual Studio) from a client application. Just remember to add mex to the end of the url to find the end point for example http://servername/_vti_bin/basicservice.svc/mex Without the “mex” you will get a HTTP: 400 internal error.