Three patients treated with bilateral subcutaneous mastectomies and implants for fibrocystic disease or carcinoma in situ subsequently developed invasive breast carcinoma. These cases emphasize that subcutaneous mastectomy does not prevent the development of breast cancer. If the circumstances in an individual patient justify prophylactic mastectomy, then the appropriate procedure would seem to be total mastectomy, which would accomplish thorough removal of all breast tissue, the subareolar region, and the nipple. Subcutaneous mastectomy for the patient who is likely to harbor occult invasive disease seems particularly inappropriate. As a means to reduce the risk of breast cancer, the procedure is unproved and must be considered an experimental therapeutic approach.