We demonstrate here two autopsy-proven cases of virilization associated with choriocarcinoma. The first patient was a 27-year-old woman with a 7-year history of metastatic choriocarcinoma who presented with left hemiparesis and virilization. Serum testosterone concentration was 18 nmol/l, free testosterone 471 pmol/l, dehydroepiandrosterone sulphate (DHEA-sulphate) 1.7 mumol/l, sex hormone binding globulin 12.3 nmol/l, estradiol (E2) 1,843 pmol/l, and hCG 1.6 x 10(5) IU/l. The second patient was a 21-year-old virilized woman with metastatic choriocarcinoma who presented in semicomatose state. Limited endocrine investigation revealed serum testosterone 27 nmol/l and hCG 2.7 x 10(5) IU/l. Both patients died despite chemotherapy and radiation therapy. Autopsy findings revealed choriocarcinoma with brain and multiple organ metastasis in both. Pathology of the ovaries of both patients demonstrated hyperplasia of luteinized theca cells and lutein cells. We postulate that an association of virilization and choriocarcinoma resulted from long-standing stimulation of ovary by hCG causing theca cell hyperplasia with subsequent hypertestosteronemia and virilization.