In training system design and acquisition, some aspect of the procurement addresses the fidelity of the training system. Normally, physical fidelity is the sole concern, although some of the more sophisticated designs and acquisitions have also looked at the concept of functional fidelity as being equal to or greater than that of physical fidelity. This emphasis on functional fidelity to two-dimensional simulation of the three-dimensional systems. Experience has demonstrated, however, that regardless of the quality of both physical and functional fidelities, a substantial number of training systems are unused, unappreciated, and unsuccessful for their planned training mission. This paper identifies a missing ingredient in the study of training system fidelity, that of psychological fidelity. Whereas physical fidelity has to do with how closely something looks like the real thing, and functional has to do with how well it acts like the real thing, psychological has to do with how well it is perceived to train like the real thing. While related to user acceptance, psychological fidelity is the environmental perception of the learner, not the instructor. Users forget that they are in training, and learn as if working with actual equipment. The elements associated with psychological fidelity are identified. Relationships between psychological fidelity and both physical and functional fidelity are specified. Directions for including psychological fidelity elements during the fidelity analysis process are provided. Finally, recommendations are given for a methodology for incorporating psychological fidelity in training system acquisition in the next decade.