Training our Army through the use of increasingly sophisticated simulations is in many ways becoming routine. The case for vehicle simulators has been well established based in large part on the relative costs of operating real vehicles versus simulators. However, the case for immersive simulators for individual soldiers is not so well established, consequently the research and development of such simulators has been proceeding slowly. This paper examines the case for individual soldier simulators relative to the cost of live exercises, the ability to build and control the training scenario, and the ability to train safely. The immediate high-benefit applications of individual soldier simulators include mission rehearsal and the development of soldier systems, and in these cases the benefits derive mainly from the ability to build and control scenarios that cannot be effectively achieved by other means. In addition, combined arms training is rapidly moving to simulators both for cost and training effectiveness as mounting large field exercises becomes more expensive and less operationally feasible. While progress has been made in individual soldier simulators, renewed research and development efforts are needed in critical areas of technology such as visual databases and locomotion simulation platforms.