Prophylactic mastectomy, intensified breast cancer screening, and the use of chemopreventive agents have all been recommended to reduce breast cancer risk in women with a family history of breast cancer. Yet, little is currently known about the efficacy of these approaches in reducing breast cancer mortality. The recent identification of BRCA1 and the localization of BRCA2 lend urgency to the need to assess breast cancer intervention and prevention strategies for women likely to carry germline mutations at these loci. At present, families with a history consistent with a BRCA1 or BRCA2 mutation should be tested within the confines of a research protocol and encouraged to participate in intervention and prevention trials. Both retrospective studies and prospective clinical trials are critically needed. While randomized clinical trials would be the optimal mechanism to assess the relative efficacy of these potential interventions, no consensus was obtained as to whether such a trial would be feasible because of strong patient preference for intervention type. It is likely that optimal intervention and prevention strategies will consist of a combined approach to risk reduction. Participants must be appropriately informed of the potential risks as well as the potential benefits of such testing. The potential risks of testing for genetic susceptibility include not only potential psychosocial harm that may result from learning one's carrier status, but also the potential for altered family relationships and insurance and job discrimination. Participants and their family members must be counseled concerning the implication of their test results.