A family history of ovarian cancer without breast cancer can be a pitfall in interpreting the high breast cancer risks. A family with high breast and ovarian cancer risks due to a BRCA1 or BRCA2 mutation, can present itself with ovarian cancer only. In three women, 43, 50 and 61 years of age, there was a family history of ovarian cancer. In the youngest woman breast carcinoma was diagnosed and she was referred for genetic counseling and DNA mutation analysis. She was identified with a pathogenic mutation in BRCA1 and decided for regular breast examination and prophylactic adnectomy. The 50-year-old woman presented with ovarian cancer and was found to have a BRCA1 mutation. She received surgery and chemotherapy for her ovarian cancer and regular examination of the breasts. The third woman at risk could be reassured, since she did not carry the BRCA1 mutation that was found in her affected sister. Because the patients and their family members can benefit from regular surveillance and prophylactic surgery, it is of great importance to identify the high breast cancer risks as well as the high ovarian cancer risks in these families.