More information is needed about the relative effectiveness of prophylactic surgery, chemoprevention, and surveillance in reducing breast and ovarian cancer risk in women with an inherited susceptibility mutation. We assessed practical and ethical barriers to conducting randomized clinical trials (RCTs) to compare preventive interventions for breast and ovarian cancer. Eighty-seven at-risk women who attended an education and counseling session about BRCA1/2 testing were asked about their willingness to participate in hypothetical research studies for breast and ovarian cancer risk reduction. In addition, 247 Maryland physicians from five specialties completed a mail survey including a question about their likelihood of recommending RCT participation to an at-risk woman. Nineteen percent of at-risk women reported willingness to participate in a hypothetical RCT for breast cancer risk reduction and 17% for ovarian cancer risk reduction. Women with children and women likely to have a prophylactic mastectomy if found to have a susceptibility mutation were significantly more willing to participate in an RCT. A majority of women would be willing to participate in nonrandomized trials or registries. Fifty-two percent of physicians responded that they would be likely to recommend RCT participation to a woman carrying a breast cancer susceptibility mutation. Oncologists were the most likely to recommend an RCT. Although the results of nonrandomized trials may be difficult to interpret because of such issues as selection bias. Greater feasibility combined with fewer ethical concerns make nonrandomized trials a more viable alternative to randomized trials for evaluation of preventive interventions for breast and ovarian cancer when prophylactic surgery is one of the treatments being evaluated.