BACKGROUND: Somato-sensory evoked potential (SSEP) monitoring has been used to help minimize neurologic morbidity during spinal surgery. However, SSEP is affected by anesthetics, technical errors and physiologic aspects. We reviewed 50 cases of spinal surgery done with total intravenous anesthesia under SSEP monitoring. METHODS: Fifty patients, ASA class I-II, free of neurologic disease and scheduled for elective spinal surgery were randomly selected for the study. All of the operations were performed under general anesthesia employing the method of total intravenous anesthesia with propofol and fentanyl (Group I, P-F) or ketamine (Group II, P-K), and monitored by SSEP. We checked the changes of blood pressure and heart rates during the operation, recorded latency and amplitude of SSEP in the pre-induction, post-induction, during screw insertion and post-distraction periods. Also, we checked the number transfers to the ICU and application of a ventilator. RESULTS: Systolic and diastolic blood pressure were increased significantly in the propofol-ketamine group (P < 0.05), but there was no difference in heart rate between both groups. In addition there were no statistical differences in latencies and amplitudes of SSEP. The number of patients transferred to the ICU and placed on a ventilator showed no statistical difference. CONCLUSIONS: We think that the combination of propofol and fentanyl or ketamine used for total intravenous anesthesia is a very useful method in spinal surgery under SSEP monitoring.