Many reactive control systems consist of classes of interacting objects where the objects belonging to a class exhibit similar behaviors. Such interacting process classes appear in telecommunication, transportation and avionics domains. In this paper, we propose a modeling and simulation technique for interacting process classes. Our modeling style uses standard notations to capture behavior. In particular, the control flow of a process class is captured by a labeled transition system, unit interactions between process objects are described by Message Sequence Charts and the structural relations are captured via class diagrams. The key feature of our approach is that our execution semantics leads to a symbolic simulation technique. Our simulation strategy is both time and memory efficient and we demonstrate this on well-studied non-trivial examples of reactive systems.