A 15-year-old phenotypic female referred for the investigation of primary ammenorrhea, was found to have a 45,XO karyotype and an ovarian cyst. She demonstrated some of the features of Turner's syndrome, as well as virilization. On laparotomy, she was found to have bilateral gonadoblastomas. She was treated with total abdominal hysterectomy and bilateral salpingo-oophorectomy. Subsequently, repeated chromosomal analysis detected the presence of Y chromosomes, which was confirmed by the use of polymerase chain reaction (PCR). The difficulties encountered in searching for the Y chromosome in patients with gonadoblastoma are discussed. Prophylactic gonadectomy is suggested in those cases associated with atypical features.