An overview of operational gaming/systems simulation. Four separate areas must be distinguished: analytic models, machine simulations, man/machine simulations, and free-form games. Analytic models are usually too abstract to solve operational problems directly, but give insights into sources of difficulty. Computer simulation appears to have been oversold; a shakedown is occurring, and many expensive simulation programs go unused. The difficulties of modeling, specification, data gathering, validation, sensitivity analysis, question formulation, and answer recognition make general-purpose simulators impossible. In man/machine gaming, people may be used because they are cheaper than software, or because human factors are being studied. Free-form gaming involves individuals acting in a scenario; other than the value of their time, costs are miniscule. Simulation costs are probably at the order of $100 million yearly. Conclusion: The future of gaming and simulation is quite good; demand is growing and technology is improving; but the growth must be controlled. 21 pp.