Answer - There are three major ways of hosting a WCF services • Self-hosting the service in his own application domain. This we have already covered in the first section. The service comes in to existence when you create the object of Service Host class and the service closes when you call the Close of the Service Host class. • Host in application domain or process provided by IIS Server. • Host in Application domain and process provided by WAS (Windows Activation Service) Server. More details http://www.dotnetfunda.com/articles/article221.aspx#whatarethevariouswaysofhostingaWCFservice