A TCT-300 scanner (manufactured by the Toshiba Co., Tokyo) has been installed in the operating room of Shinshu University Hospital since 1986. This neurosurgical operating CT scanner system was developed for obtaining intra- and postoperative CT images in the operating room. We have carried out immediate postoperative CT scanning in 206 cases: 170 were major and 36 were minor operations. A mobile CT scanner gantry has been used in 125 cases since June, 1988. We obtained CT images immediately after surgery on the digitalized operating table, the motion of which can be controlled as with the conventional CT scanner table. Immediate postoperative CT scans showed the extent of removed tumors or hematomas, position of the tip of ventricular or cisternal tubes, injury to the surrounding normal brain caused during the removal of lesions, and postoperative complications such as hemorrhage, brain swelling and surgical patties which had been inadvertently left in the wound. This CT scanner system in the operating room proved to be useful in the postoperative care of neurosurgical patients.