BACKGROUND: Contralateral prophylactic mastectomy (CPM) is the removal of a nonaffected breast in a woman with unilateral breast cancer and is effective in reducing the risk of recurrences. Little is known about women’s decision-making roles regarding CPM. METHODS: Women aged 18-80 years with CPM performed at one of six health maintenance organizations between 1979 and 1999 were surveyed. We determined women’s reported decision-making roles at the time of CPM, analyzed their trends over time, and explored the association between decision-making roles and psychosocial outcomes following CPM. RESULTS: We received 562 responses (response rate = 73%); 431 completed items needed for this analysis. Most respondents were white, younger than 55 years at CPM, married, and had CPM within 10 years of completing the survey. Forty-five percent made the decision to undergo CPM alone, 37% considered their doctor’s opinion, 15% shared the decision with their doctor and only 3% reported their doctor primarily made the decision. Women reporting active roles were more likely to be younger (P<.0008), college educated (P<.0001) and have CPM more recently (P = .002). Compared with those sharing the decision with their doctors, women with active roles were twice as likely to be satisfied 6 months following CPM (odds ratio [OR] = 2.2, 95% confidence interval [CI] = 1.1 to 4.2) and report current concern about breast cancer (OR = 1.9, 95% CI = 1.0 to 3.4). CONCLUSIONS: Most women reported active or shared roles in decision making regarding CPM, particularly younger women, those with college education, and those with recent CPM. Women with active roles were more often satisfied in the short term but were also more likely to report current concern about breast cancer. Whether higher concern is related to insufficient input from clinicians should be explored. Prospective data are needed.