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Four meningiomas were scanned during surgery using a commercially available, real-time sector sonographic scanner. Each lesion was ext remely well defined, and its effects on the surrounding brain were easily characterized by su rround ing edema and displaced ventricles. In one case, sonography demonst rated the nonresect ability of a portion of the tumor because of involvement of the superior sagittal sinus. Th is preliminary experience suggests sonographic imaging may be useful during the resec-tion of meningiomas. There has been some interest in intraoperative sonographic locali zation of brain tumors in the past [1-4]. However, these one-dimensional displays could only determine the depth of the lesion and crudely eval uate its echogenicity. The internal characteri sti cs, the boundari es, and the effec ts of a les ion on normal structures were almost impossible to evaluate. We have been using real-time, two-dimensional, gray scale sonog raphic scanning int raoperati vely to define intracranial pathology [5, 6]. These scans can give quite accurate representations of both normal and patholog ic anatomy. The va lue of thi s technique is in reducin