Treatment results for 36 patients with juvenile pilocytic astrocytoma treated from 1942 through 1985 at the University of California, San Francisco, were reviewed. Twenty-two tumors were located in the posterior fossa, 10 were in the hypothalamic region, and four were in the cerebral hemispheres. Twenty-eight patients were less than 18 years of age. The overall survival rate was 83% and 70% at 10 and 20 years, respectively. All 12 patients who had total tumor resection remain disease-free; only two of the 12 received postoperative irradiation. The 10- and 20-year freedom-from-progression for the 19 patients who had incomplete resection and received at least 40 Gy of postoperative irradiation was 74% and 41%, respectively. All patients who failed treatment had local recurrence. One patient developed diffuse meningeal seeding, after four local recurrences in the posterior fossa over a 23-year period. Six patients failed treatment and had a repeat biopsy at the time of recurrence or at postmortem examination, and three showed histological progression of the tumor to an anaplastic astrocytoma. Based on this study and others in the literature, a protocol has been adopted whereby patients who have total tumor resection are not treated with postoperative irradiation. Patients who have incomplete tumor resection and are older than 3 years of age are currently treated with postoperative partial-brain irradiation, to a dose of 45 to 60 Gy. In general, young children with incomplete resection are followed closely with computerized tomography or magnetic resonance imaging and are treated with chemotherapy or irradiation if tumor progression is documented.