"Translation" of the current "basic science" information related to physical activity into patient intervention programs is needed. This translation is critical to providing benefit to the maximum number of patients. Little is known about the determinants of physical activity among breast cancer patients undergoing hormonal therapy and few studies have attempted to evaluate an exercise behavior change program aimed to improve exercise adherence among such patients. The proposed project will evaluate use of an innovative behavioral and psychosocial intervention to increase physical activity among breast cancer patients.