This chapter considers a number of practical implications of the distinction between implicit and explicit learning. Two obvious areas of interest are training people and assessing what they have learned. The chapter discusses the problem of implicit knowledge in the context of the development of expert systems. It also considers some other areas where the implicit-explicit distinction has been applied. These include human computer interface design, second language learning, social cognition, and playing golf and other ball games. Empirical studies have tended to focus on the effectiveness of different methods of training for the instruction phase, and they have been primarily concerned with comparing different forms of explicit learning. A related issue that is relevant to training is determining the best order of combining implicit and explicit training phases. Even when people attain expertise in a particular domain, knowledge assessment is still important, particularly since the development of computer-based expert systems.