This is a report of ovarian carcinoma occurring in two sisters diagnosed almost at the same time, prompting prophylactic oophorectomy in a third sister. Histology of the overtly normal ovary in the third sister showed a focus of ovarian cancer. Discussion and a review of the literature suggest that any program designed to reduce the incidence of late-stage ovarian carcinoma should include the surveillance of family members of the index case, including the performance of prophylactic oophorectomy in the unaffected members of the family after they have completed their families.