Parallel discrete-event simulation research has focused mainly on designing efficient parallel simulation protocols. However, the exploitation of parallel simulation technology in real-life applications has been hindered mainly by the lack of simulation support tools. This paper describes the design of SPaDES (Structured Parallel Discrete-Event Simulation), a parallel simulation environment for developing portable simulation models, and a platform for design experimentation of parallel simulation synchronization protocols. An implementation of the environment, SPaDES/C ++ , cleanly separates simulation modeling and programming from the details of parallelization such as parallel simulation synchronization and parallel programming. For ease of portability and modular design, SPaDES/C ++ is implemented as a parallel simulation library. A comparison of SPaDES/C ++ with CSim and Simscript using two application examples is discussed.