The present invention provides for routing calls between disparate domains, such as a circuit-switched subsystem and a multimedia subsystem. When a user element is homed in a first domain and roaming in a second domain, an incoming call will arrive at a gateway node in the first domain. As a result, a message identifying the user element and indicating that an incoming call has been received at first gateway node for the first domain is sent to a continuity control function (CCF) residing in the multimedia subsystem. The CCF will create and effect delivery of an inter-domain routing number to the first gateway node. The inter-domain routing number is used by the first gateway node to route the call to the second domain. The inter-domain routing number may be associated with a second gateway node of the second domain.