In this chapter, we have discussed the design of parallel simulators of data parallel programs, and used a simulation engine, DPSIM, to prove the usefulness of the proposed techniques. We have shown that the communication patterns generated by data parallel programs can be easily simulated, without costly runtime simulation mechanisms. Hence, we have achieved excellent slowdowns which, although application dependent, have been brought to as close as 1.06 of the actual application. Also, we have shown that conservative simulation techniques can be effectively used to parallelize simulations. We have achieved a speed up of as much as 11 by increasing the processors in the simulation from 1 to 16.