BRCA2 germ-line mutations confer an increased risk of developing breast and ovarian cancer. We report the occurrence of a mixed ovarian germ cell tumor (GCT) (50% embryonal carcinoma, 20%-25% choriocarcinoma, 10%-15% dysgerminoma, and 10%-15% immature teratoma) in a 33-year-old Ashkenazi Jewish woman, carrier of the BRCA2:6174delT mutation. The mutation is also present in the patient's father, who was diagnosed with breast cancer at age 59 and with prostate cancer at age 69. This is the first report of a GCT in a BRCA2 mutation carrier; there was one previous report of an ovarian dysgerminoma in a BRCA1 carrier. Molecular analysis of the proband's tumor DNA revealed there was no loss of heterozygosity of the wild-type allele in the tumor, as is usually the case for epithelial BRCA-related ovarian tumors. This suggests either that biallelic inactivation of BRCA2 is not required for GCT development or that this is a chance event unrelated to the presence of the mutation.