BACKGROUND The treatment of brainstem gliomas remains controversial. This article focuses on surgical results. METHODS The authors retrospectively analyzed 35 patients with primary midbrain gliomas who were treated at Beijing Neurosurgical Institute from 1986 to 1997. The diagnosis was verified by histological examination. RESULT The incidence of midbrain glioma was 10.3% (35/340) in our patients with brain stem tumors. The 35 gliomas were classified into three therapeutic groups by their locations: 7 were located in the tectal region, 8 in the aqueductal region, and 20 in the tegmental region. All of the patients underwent microsurgical treatment based on a minimally invasive approach. The operation took the form of total resection in 19 cases, subtotal resection in 12, and partial resection in 4. The operative mortality was 0, With a mean follow-up of 28 months (range, 6-48 months), 65.7% (23/35) of patients could live independently. CONCLUSION The volume and location of midbrain tumors were highly correlated with outcome. The resection of as much tumor as possible was optimal for the treatment of midbrain gliomas and radiotherapy after operation was beneficial to patients. (C) 2000 by Elsevier Science Inc.