This paper presents a scenario-based implementation architecture supporting a method capable of automatically mapping real-time object-oriented models into multi-threaded implementations. To implement the synthesis tool supporting the method, we exploit existing CASE tools that support the object-based implementation architecture. Challenges in our approach are (1) how to embed our implementation model into generated design-model-dependent code and (2) how to implement the model-independent run-time-system library.In our approach, to map each scenario to a thread, we make external messages starting scenarios delivered to their mapped physical thread. The main operation of the thread is (1) waiting for any external message to be delivered and (2) executing a while loop where all internal messages are sent and received. The state transition of an active object is guarded by an object-specific mutex to maintain the run-to-completion semantics. The priority of a thread is dynamically set according to the scheduling attributes of an external message for the thread to process.