The Speed-CS Project at the University of Arizona is creating a workbench that will facilitate rapid composition, evaluation, modification and validation of applications of distributed computing technology.  Advances in procesor technology have made it possible to bestow computational  and communications power to devices ranging from simple sensors to more complex control and decision systems. Despite the phenomenal growth in applications of distributed computing systems, it is safe to suggest that we have only begun to scratch the surface. We expect a proliferation of systems consisting of heterogeneous, geographically distributed platforms that operate intelligently, communicate reliably and can be reconfigured easily. Unfortunately, current software support is often limited to isolated models and simulations.  As a result, we are severely restricted in our ability to assess system performance and reliability.  The SPEED-CS project is addressing this growing need.