This chapter considers the design of training environments, and motivations for using virtual environments (VE). In the perceptual-cognitive skills area there are also systems that have some similar characteristics, use many of the same technologies, and are employed for sport training but do not meet the definition of a VE. The potential advantages of using a VE for training perceptual-cognitive skills in sports can be seen by looking at some of the evidence-based principles that have been proposed for practice design. When assessing the effectiveness of a sports training VE, it is essential to separate primary and secondary evaluation criteria. Psychological fidelity refers to the extent to which a VE recreates the perceptual-cognitive demands of the real task and leads to similar behaviours being observed from the user as in the real environment. Given the evidence for specificity of practice, it is likely that psychological fidelity is more strongly related to transfer of training than physical fidelity.