Abstract Background: A germline mutation in the BRCA1 or BRCA2 gene predisposes for breast- and ovarian cancer. Female carriers of a BRCA-mutation ≥ 25 years of age, need to choose between surveillance and prophylactic surgery for their breasts and ovaries. Until now it remains unclear which factors contribute to these choices. Aim: The aim of our study was to investigate whether psychosocial or care provider-related factors influence the choice for prophylactic surgery in BRCA mutation carriers. Design: The cohort consisted of 635 women (mean age 46 (18–90) years), all living in the South East of The Netherlands and counseled between 1994 and April 2012. 323 women were carrier of a BRCA1 and 312 of a BRCA2 mutation. 239 had breast cancer, 38 ovarian cancer, 28 had breast and ovarian cancer and 330 women had no cancer history. Univariable and multivariable logistic regression analyses were performed with either breast surveillance vs. mastectomy or ovarian surveillance vs. bilateral salpingo-oöphorectomy (BSO) as outcome. The following factors were investigated: – Personal: age at time of BRCA test and cancer history,– Familial: presence of first degree relative with breast and/or ovarian cancer, age of the relative and the BRCA carrier at time of cancer diagnosis in this relative, whether the BRCA carrier had children and if so age of the children(< 18 or ≥ 18),– Counseling: professional responsible of counseling (clinical geneticist vs genetic counselor), Psychsocial support (if needed) (genetic counselor vs psychologist) and whether the follow up was in specialized multidisciplinary teams or a peripheral hospital. Results: Prophylactic mastectomy was chosen by 132 of the women, breast surveillance by 352 women. BSO was chosen by 268 women, most of them above 40 years of age; ovarian surveillance by 161 women. Ovarian surveillance was the choice of women younger than 40, women with a breast cancer history and older women. Univariable analyses revealed that women more often chose for mastectomy when they had a younger age (OR 0.94 CI 0.919–0.964), breast cancer (OR 4.827 CI 2.843–8.198), children (OR: 1.889 CI 1.085–3.289), especially children under the age of 18 (OR 1.778 CI 1.103–2.866), a first degree relative with cancer (OR 0.41 CI 0.231–0.728) or consulted a psychologist (OR 5.299 CI 1.425–19.703). The choice for mastectomy was not influenced by the counselor or the place where the follow-up was given. Multivariable analysis showed that if all factors were considered together, 3 factors remained significant for choosing mastectomy: age, personal cancer history and first degree relative with cancer factors. No factors were found that influence the choice for preventive measures for ovarian cancer. This was expected because since 2002 all women BRCA carriers where advised to chose BSO above 40 years of age. Conclusion: Personal and familial factors play important roles in the choice for prevention of breast- and ovarian cancer in female BRCA mutation carriers. In our study counseling factors, such as type of counselor or place of follow-up did not influence the choice for prophylactic mastectomy. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-08-02.