The present document provides a set of interoperability use cases to be tested in order to validate an interconnection between IMS and EPC subsystems. For each use case there are conformance criteria and Test Descriptions (TD) detailed. The target of the present document is to provide the boiler-plate for verifying interoperability between the IMS and EPC subsystems based on the exemplary scenarios network attachment@ IMS registration and IMS session management@ IMS de-registration and network detachment. Each scenario is covered for both single n/w and roaming.