This article describes a neuropsychological theory of motor skill learning that is based on the idea that learning grows directly out of motor control processes. Three motor control processes may be tuned to specific tasks, thereby improving performance: selecting spatial targets for movement, sequencing these targets, and transforming them into muscle commands. These processes operate outside of awareness. A 4th, conscious process can improve performance in either of 2 ways: by selecting more effective goals of what should be changed in the environment or by selecting and sequencing spatial targets. The theory accounts for patterns of impairment of motor skill learning in patient populations and for learning-related changes in activity in functional imaging studies. It also makes a number of predictions about the purely cognitive, including accounts of mental practice, the representation of motor skill, and the interaction of conscious and unconscious processes in motor skill learning.