Reactive systems have been defined as systems that maintain an ongoing relationship with their environment. The behavior of deliberative systems can be described as computing a function from an initial state to a terminal state. Reactive programming leads to a new programming style supporting a logical notion of time corresponding to instants where programs react. Examples of pure reactive systems include man-machine interface handlers or computer games. Most time critical applications have to include a reactive behavior to meet their timing constraints, and a deliberative behavior to face the new requirements of highly sophisticated, complex and distributed real-time systems (air traffic control, nuclear plant control, embedded tactical systems for military applications). We describe a simulation environment providing facilities for designing time-constrained distributed applications involving a mixed reactive/deliberative behavior, The simulator runs on a Sun4 IPX workstation under the Unix operating system and an X-Window graphical interface. This work is supported by the French Ministry of Defense (DRET).