Dataflow languages and processors are currently being extensively studied because of their respective ability to specify and execute programs which exhibit a high degree of parallel and/or asynchronous activity [12, 7]. This paper describes a comprehensive simulation environment that allows for the execution and monitoring of dataflow programs. One overall objective of this facility was to meet the needs of researchers in such diverse areas as computer architecture, algorithm analysis, and language design and implementation. Another objective was to accommodate the semantics of several of the contending abstract dataflow models [2, 4]. Additionally, it was desired to enhance the abstract dataflow models which the simulator would support. These objectives, combined with the desired debugging and metering requirements, directed the design of the overall system. A brief introduction to dataflow and its related terminology is given to assist the reader. A companion paper [6] describes an augmentation to the basic simulation facility presented here that allows for the execution of dataflow programs on processors having finite resources.