Histologic classification and treatment of pediatric cerebellar astrocytomas is an area of controversy. At the Medical College of Wisconsin, 34 patients less than 15 years of age (median, 7.3 years of age) with cerebellar astrocytomas were seen from 1965 to 1988. Effect of histologic condition and treatment on overall survival (0s) and progression-free survival (PFS) was analyzed. Progression was defined as radiographic evidence of an enlarging mass and/or signs and symptoms indicative of advancing disease. Histologic material was reviewed and classified by the system of Winston and Gilles. Twenty-eight patients had glioma A tumors, and six patients had glioma B tumors. For patients with glioma A (n = 28), 5-year actuarial 0s rate was 100%. For patients with glioma B (n = 6), 5-year acturial 0s rate was 41D/o. PFS rate was 66% and 0% for patients with glioma A and glioma B, respectively. The poorer PFS for patients with B histologic tumors was statistically significant (P less than 0.001). The median time to progression was 36 months and 23 months for patients with glioma A and B, respectively. Patients were retrospectively divided into total resection and observation, total resection and irradiation, subtotal resection and observation, and subtotal resection and irradiation groups, which were composed of 12, 2, 3, and 1 7 patients, respectively. Five-year actuarial 0s rates were loo%, SO%, 50%, and loo%, respectively. PFS rates were SOYO, 50ยฐ/o, 33%, and 58%, respectively. These data support the Gilles classification as a prognostic tool because patients with B tumors had a higher incidence of disease progression and accounted for all deaths. Postoperative irradiation after subtotal resection seems to be beneficial, but additional investigation, ideally with a prospective randomized trial, will be necessary to firmly establish this. Cancer 67: 2772-2775,1991. HE CENTRAL NERVOUS SYSTEM (CNS) is the second T most common site of neoplasms in children. The infratentorial region is the most frequent site of CNS neoplasms in the pediatric population. Cerebellar astrocytoma ranks second only to medulloblastoma in frequency of occurrence.' Despite being relatively common, a fair amount of confusion exists regarding their histopathologic classification and treatment.