This article reviews the current state of knowledge regarding factors which put women at highest risk for developing breast cancer and identifies that population we consider as potential candidates for prophylactic mastectomy. Specifically, we focus on the concept of cumulative predisposition and the relative risk assigned to more significant factors that increase a woman's chances of developing breast cancer: family history, proliferative breast histology, and previous cancer in one breast. In addition to outlining the results of reconstruction, the article also examines the controversy surrounding the issue of whether any mastectomy can be truly prophylactic. We conclude with advice to physicians who must counsel women concerned about their breast cancer risk so they can help their patients make fully informed choices.