BACKGROUND: Monitoring the skin temperature changes of the palm during video endoscopic thoracic sympathicotomy has been used as a measure of the success of the surgery. When general anesthesia is used during sympathicotomy, increases of skin temperature on the ipsilateral palm is less than that observed in percutaneous chemical sympathectomy. Contralateral skin temperature has been found to be decreased. So we measured palmar skin temperature on both sides during sympathicotomy to learn whether we can use it as a indicator of success under general anesthesia, and to see contralateral sympathetic responses. METHODS: Thirty patients have been examined. The skin temperature of both their thenar areas was measured before sympathicotomy, and 5 and 10 minutes after sympathicotomy under general anesthesia, using N2O, O2, enflurane, vecuronium. RESULTS: Under general anesthesia, there was a significant increase of post-sympathicotomy skin temperature on the ipsilateral palm, in contrast to a decrease on contralateral ones. The absolute value was minimal but statistically significant. CONCLUSIONS: Thoracic sympathicotomy may producc simultaneous but different types of sympathetic response on both sides of the hands, though this response is lessened with a use of general anesthesia because inhalation anesthetics induced central and peripheral sympathetic inhibition. We conclude that continuous and careful monitoring of palmar skin temperature yields useful information about intraoperative success during thoracic sympathicotomy under general anesthesia and that we should conduct further study of the contralateral sympathetic response.