The authors, instructional technology faculty at a large Eastern university, described the design of computer-based simulations in terms of three major aspects: the scenario, the underlying model and the instructional overlay, with major emphasis/focus on the instructional overly. They presented a feature-function map of a general model for simulation development and discussed each aspect of their proposed model. They also discussed/presented variations on the general model for specific types of content as well as proposing prescriptions for the nature of stimulus and response for practice cases with several types of simulations. The authors stated that their theory was designed to provide a useful framework for conceptualizing research studies and the theory needed further research/revision. A structured, validated research study with some statistical data would have been a valuable addition to this theoretical article. Provided theory background for the development of computer based simulations.