Forty-two patients with supratentorial gliomas not involving the basal ganglia (extraganglionic) were studied pre- and postoperatively with computed tomographic (CT) scans to evaluate the effect of the extent of surgical resection on the immediate postoperative results. Thirty-three patients (79%) had malignant astrocytic gliomas (glioblastoma or anaplastic astrocytoma), 4 patients (10%) had well-differentiated astrocytomas, and 5 (12%) had oligodendrogliomas. The median age was 58 years, and the median Karnofsky rating was 70. There was no operative mortality. Six patients (14%) had surgical complications. A gross total resection was defined as the absence of any abnormal enhancement on the postoperative CT scan. A nearly gross total resection had been accomplished when less than 10% of the preoperatively enhancing mass was still seen. A partial resection was indicated by the presence of more than 10% of the enhancing lesion on the postoperative CT scan. A gross total or nearly gross total resection was accomplished in 36 patients (86%), and an improved or stable postoperative neurological status was present in 35 of these patients (97%). In contrast, the rate of neurological morbidity after a partial resection was 40%. Supratentorial extraganglionic gliomas, regardless of their histological type, generally were well-circumscribed lesions except at the level of the ventricular wall, where glioblastomas and anaplastic astrocytomas blended with the subependymal white matter from which they seemed to arise.