OBJECTIVE: An usefulness and an accuracy of Neurosurgery Simulator(R)(NSS(R)) is evaluated for the clinical applications. The NSS(R) is a surgical planning tool for stereotactic and functional neurosurgery, recently developed in Korea. METHODS: Thirty-four surgical cases, performed with the NSS(R) from October 1999 to April 2002, were analyzed. The accuracy was examined by comparing the actual lesion with the planned target. The usefulness was discussed with time consuming factor and convenience for surgical steps. Results of surgical outcome were also reviewed. RESULTS: The precise coordinates of surgical target is directly acquired by designating an anatomical lesion on the magnetic resonance image with NSS(R) due to auto recognition algorithm of the fiducials on the MRI image. The correctness is confirmed again by examining the anatomical lesion with superimposing the Schaltenbrand-Wahren atlas on the image directly. Among eleven cases of the thalamotomy for tremors, five cases resulted in complete resolution, the remaining five patients showed significant reduction of tremors. Improvement of ADL and UPDRS was recorded in all 6 Parkinson's disease patients who had undergone pallidotomy. Seventy five percent of patient in pain and psychosurgery resulted in improvements. The NSS(R) achieved 100% accuracy in calculating stereotactic biopsy coordinates. There was no deviation in guiding surgical trajectory. There was no significant surgical complication. CONCLUSION: Stereotactic and functional neurosurgery performed with the assistance of the NSS(R) is relatively safe and accurate.