The experience of the Radiotherapy Service, Clínica Puerta de Hierro, Madrid (Spain), in the treatment of intracranial tumors with risk of neural axis dissemination is analyzed. In 15 years (1964-1979) 415 primary central nervous system tumors were studied and treated; 67 corresponded to tumors with risk of meningeal dissemination. Clinical dissemination in cerebrospinal fluid was proven in 14 patients. The actuarial survival of 10 years for patients with neural axis dissemination, without prophylactic treatment to the neuroaxis, is 14% with an average survival of 10.5 months. In approximately 20% of meduloblastomas, ependymal and pineal region tumors, meningeal metastases at some distance from the primary tumor can take place. Patients at risk with these types of neoplasia must be identified, and an adequate radical therapeutic focus devised, not only for the primary tumor, but also for the risk of dissemination. © 1983.