This paper reviews the recent experimental and theoretical literature regarding adaptation to the wearing of prisms that laterally displace the visual field. Emphasis is placed upon adaptational changes in proprioception, the development of new patterns of muscle efference, and the interaction between such changes in proprioception and efference. The paper also includes a discussion of prism adaptation as a learning process which acts to minimize disparities between different sensory modalities. In this context, information, attention, judgment, and experimental design are .treated as imposing important constraints upon which sensory inputs are accepted as veridical. The role of classical conditioning and the importance of active movement are also discussed.