Object oriented simulation is becoming more and more important, as object based software architectures and platforms are gaining popularity. A prototype CASE environment is under development at CSELT which allows users to specify applications according to the ACE computational model, an object oriented based on the concept of Building Block, in turn derived by the TINA-C architecture. One of the features provided by ACE environment is the simulation of the specifications. The proposed approach to simulation is to first translate the object oriented specification to the process level, to use an already available simulation engine with a good efficiency and reliability and then bring the simulation results back to the object level. The semantics of the ACE language, which includes sophisticated primitives, like asynchronous method invocation, concurrent objects and method guards has been mapped at the process level using appropriate templates. The results show that a good efficiency has been obtained: around one hundred object level events per second are simulated on a state of the art workstation.