The most common breast complaint presented to primary care and breast clinic providers is pain, and the majority of such pain is cyclical. Cyclical mastalgia is poorly understood, inadequately assessed, and not systematically treated in the United States, although it is a recognized, and commonly treated disorder in Britain. Over 60% of premenopausal women regularly experience some premenstrual breast discomfort. Approximately 10-15% of these women have clinically significant mastalgia each month, which can interfere with usual activities and is associated with elevated use of mammography among young women. The etiology of cyclical mastalgia and its relationship to other disorders have not been established. Well-substantiated effective treatment options are somewhat limited, often associated with adverse effects, and rarely prescribed by physicians in the United States. This article reviews the literature on the prevalence, impact, etiology, assessment, relationship to other disorders, and treatment of cyclical mastalgia, including recent findings from research in our Obstetrics and Gynecology clinic and Comprehensive Breast Care Center. Approaches to assessment and management are suggested, as are directions for further research. We suggest that understanding and effective management of cyclical mastalgia will be fostered by a systematic biopsychosocial, interdisciplinary approach to research.