Mental imagery, an internal representational process that enables an individual to experience an event in imagination, has been used effectively in treating psychological conditions, changing behavioral patterns, and altering physiological processes. Research on the psychological effects of imagery has focused on the influences imagery has on psychodynamic processes, self-concept and locus of control, and depression. Imagery has been used extensively in the behaviorally-oriented therapies and has proven to be a powerful intervention in treating various phobias and anxiety disorders, modifying habits, and improving motor skills. Imagery has been shown to be an effective adjunct in the medical field as well, particularly in the treatment of cancer and certain dermatological conditions. It appears that through their own mental activity, patients can have an important influence on the course of their disease and its treatment. Research has indicated that there are differences in how vividly people can image and that people who can image more vividly are better candidates for imagery therapies. Findings also suggest that it is valuable to match clients with certain characteristics to imagery techniques that specifically suit those characteristics. Guided imagery should be viewed as an adjunct to major treatment modalities which can assist in diagnoses, uncover unconscious issues, restructure thinking patterns, expand conscious experience, build internal resources, and guide certain biological processes. A three-page reference list concludes the paper. (NB)