Nineteen intracranial germ cell tumours treated during the past 11 years were evaluated retrospectively. The tumours were classified into three groups according to the level of alpha-fetoprotein (AFP) and beta-human chorionic gonadotropin (HCG) in serum and cerebrospinal fluid, and the optimal treatment for each group was determined. Group A consisted of patients with normal titres of AFP and HCG, group B of patients with relatively high titres (< 10 times normal), and group C comprised patients with higher titres ( 10 times normal levels). In group A, an appropriate field and dose of irradiation was necessary to prevent craniospinal dissemination. In group B, none of four patients who underwent total or subtotal resection of the tumour had craniospinal disseminatio n or tumour recurrence, whereas dissemination occurred in four further patients, including two who had received radiochemotherapy only, and two who had undergone partial resection of the tumour. While patients in group C had dissemination at the time of initial diagnosis, most patients in group B developed dissemination more than 10 months after initial treatment, suggesting that the type of treatment received as first line therapy is important in patients in this group. The prognosis of patients in group C, however, was unaffected by the priority given to either surgery, radiation or chemotherapy as first line treatment. Craniospinal dissemination can be prevented in patients with germ cell tumours who have a relative increase in levels of AFP and HCG by aggressive removal of the tumours as first line therapy, regardless of the type of adjuvant therapy given.