The clinical and anatomic pathological findings in 23 patients with histologically proven brain stem glioma were reviewed. Eleven patients had malignant tumors (astrocytoma, grade III, and glioblastoma multiforme) and the remaining had low grade ones. The primary site of the tumor was the pons in 15 of 21 patients examined, followed by the medulla oblongata and midbrain. Continuous cephalad and caudad involvement of pontine tumors was evident in 14 patients, and was more extensive in the high grade gliomas. At autopsy, the tumor spread via the CSF was observed in all patients with high grade but not low grade tumors. Open surgical posterior fossa exploration was performed on 12 patients. Volume reduction, by partial removal of the tumor and/or by cyst evacuation, was performed on seven, with good results. Nineteen patients were given radiation therapy, with temporary improvement of the clinical conditions. While none of the patients with malignant tumors survived more than 15 months after diagnosis, those with low grade tumors had a five-year actuarial survival rate of 50.0%, and three survived more than ten years after the diagnosis. Our data indicate that brain stem gliomas are not a homogeneous group of tumors as far as the clinical and pathological features are concerned. This heterogeneity shows the need to design specific treatments for these tumors.