Serum levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (HCG) and carcinoembryonic antigen (CEA) were determined by radioimmunoassay in 14 patients with primary intracranial germ cell tumors in the pineal and/or chiasmal region and the relationship between AFP, HCG and CEA levels, tumor histopathology and survival time was studied. In 7 of the 14 patients, elevation of AFP and/or HCG was noted. Histopathological diagnosis of these patients was embryonal carcinoma (1), choriocarcinomas (2) and seminoma (4). Five of the 7 patients died within 2 years after diagnosis in spite of surgery and/or radiation therapy. Seven patients who showed normal AFP and HCG levels consisted of 6 germinomas and one teratoma. Four of the 7 patients remain alive and well more than 5 years after surgery and/or radiation therapy. CEA was above normal in only one patient with a seminoma. Our results suggest that the serum levels of AFP and HCG are useful for predicting tumor histopathology and the prognosis of patients with primary intracranial germ cell tumors.