The present review encompasses approximately twenty years of research in computer-based training. This includes the initial development of these training systems based on behavioral principles to more recent efforts that incorporate cognitive approaches to learning. The studies that will be included in this review are organized into three groups or clusters based upon their training application. The three clusters include computer aided instructional systems used in training programs, computer aided instruction supplemented with adjunct modes such as simulation and interactive graphics, and lastly, simulators as computer-based training systems. Following an initial discussion of the foundations of computer assisted training systems in behavioral science, the more recent cognitive approaches to this training area are addressed to identify the system components that determine an effective computerized training program. The research is then evaluated and discussed according to: 1) how the systems are designed; 2) how effective the training systems are in attaining specified learning outcomes; and 3) how methodologically sound the conclusions are. This article concludes with an overall integration of the research on computer-based training, specifically focusing on what kinds of learning are being promoted most efficiently and effectively, and which factors in the systems' designs lead to most direct attainment of training goals.