A retrospective review of 86 adults (age 15 years or older) treated from 1950 to 1979 for well-differentiated astrocytoma or anaplastic astrocytoma of the cerebrum at Washington University Medical Center-Barnes Hospital was undertaken to determine the influence of postoperative radiation therapy on survival and neurologic function. Analysis was facilitated by a temporal change in treatment approach, with reliance on surgery alone before 1960 and routine use of postoperative irradiation after 1970. Six patients had astrocytomas with a juvenile pilocytic histologic pattern. Outcome was uniformly favorable in these cases regardless of therapy (100% survival; median follow-up, 14 years). Actuarial survival for the 80 patients with diffusely infiltrating astrocytoma was significantly better with the addition of postoperative irradiation than with surgery alone (median survival, 5 versus 2.2 years, respectively; 5-year survival, 50% versus 21%, respectively). Posttreatment neurologic function was also superior in the group managed with surgery and postoperative irradiation. The relationship to survival of age, degree of histologic anaplasia, extent of surgical resection, tumor size, and radiation dose was also investigated.