Today’s systems are more complex than ever before posing monumental challenges for training. Computers can be used to improve training of complex tasks and simulate complex scenarios for the purpose of task rehearsal. They have an inherent appeal and can produce immersion into the training environment. Because of these characteristics, computerbased training systems can give the illusion of training, but without sound learning principles they can be ineffective. Training systems, whether computer based or not, must be founded on empirically derived principles of learning. Here a review of metrics for evaluating training systems will be followed by a short review of training principles and a summary of guidelines and recommendations.