A case of bilateral gonadoblastoma in a phenotypic female with 45,X/46,XY gonadal dysgenesis is presented. Hormonal investigations revealed that serum testosterone, estradiol and beta-human chorionic gonadotropin decreased following excision of the tumors, but follicle-stimulating hormone and luteinizing homrone levels increased further. Immunohistochemical staining for testosterone and estradiol was positive in both Leydig and lutein-like cells in the tumor. It is suggested that gonadoblastoma is capable of producing testosterone and estradiol, and Leydig or lutein-like cells may be the actual source of these steroid hormones.