Method invocation using IIOP is the same as most other method invocation techniques. IIOP primarily defines the marshaling and transport semantics of method invocation. The OMG has defined a standard IDL-to-Smalltalk selector mapping to which SST conforms. Incoming IIOP requests are unmarshaled, their receiver identified and their operation name converted to a Smalltalk selector. Then the resulting request is forwarded as a normal Smalltalk message.

Most of SST request dispatching models (such as Threaded and Pooled) are applicable with IIOP. The one exception is the Logical Process model. In general, IIOP is used in heterogeneous environments involving different programming languages. The LP model depends on having SST running at all points in the system. As such, IIOP and the LP model are incompatible.