Various extensions of a stochastic model illustrating the spread of virus epidemics have been simulated. As assumptions and hypotheses concerning the basic model have been added and tested, the computer programs designed to run the simulation have increased in complexity. With this increase it has been necessary to reduce the amount of time and effort involved in setting up computer runs. Default parametric values, alphanumeric coded control cards, different levels of trace options, and simplified summaries have enabled these model extensions. Studies have been conducted on the effects of varying vaccination schedules, contact rates, the interference phenomenon and population composition. Future models have been defined to investigate more complicated transfer patterns and withdrawal from population mixing of those cases in whom illness may result from infection, as for influenza. These studies have been of value to epidemiologists and have encouraged the continuing design of alternate models of a more specific and complex nature.