Intraoperative ultrasonography was conducted in 52 cases of spinal tumor, at 7.5 MHz, mainly by means of linear scanning, to evaluate its clinical usefulness. The procedure was effectively applied in such clinical purposes as: 1) locating the tumor, 2) deciding the resectability of intramedullary tumors, 3) deciding the site for intraspinal biopsy or shunt tube insertion, 4) establishing the topical relationship between the spinal cord and the tumor, and 5) differentiating neurilemoma from meningoma. Of 10 patients with intramedullary tumors, 5 (50%) were removed, because extirpation was possible when the spinal cord and the tumor were well demarcated on the ultrasonogram. Intratumorous cysts were found to exist in 73% of neurilemoma and 14% of meningioma cases, enabling the differential diagnosis between the two tumors. Intraoperative ultrasonography is an uninvasive method to reveal intradural and extradural conditions and thus constitutes a valuable diagnostic means to ensure safe and precise spinal surgery.