BACKGROUND: A right thoracoscopic thoracic sympathicotomy involves the removal of T2 and T3 sympathetic chains. Since part of the sympathetic fibers to the heart traverse these two ganglia, we examined the hemodynamic changes during a thoracoscopic thoracic sympathicotomy in primary hyperhidrosis. METHODS: Noninvasive cardiac output monitoring was done on the both side of the neck and chest. A physiograph for measuring of continuous blood flow was taken from the right index finger and a thermometer was placed in the right palm. Following endotracheal intubation was done with double lumen endotracheal tube, anesthesia was maintained with isoflurane. Sympathicotomies were done for T2-3 during one lung ventilation. Heart rate (HR), mean arterial pressure (MAP), systemic vascular resistance index (SVRI), cardiac index (CI), accelerated contractility index (ACI), end-diastolic index (EDI), and temperature were recorded at arrival, before sympathicotomy, after sympathicotomy at 1, 2, 3, 4 and 5 minuets. The blood flow of the right index finger was recorded before and after the sympathicotomy. RESULTS: Concurrent with initiation of the sympathicotomy, MAP and SVRI were reduced, but the CI was elevated. It was accompanied with right palmar temperature elevation and an increase in the blood flow of the right index finger. CONCLUSIONS: A thoracoscopic thoracic sympathicotomy reduces MAP and SVRI and elevates CI, palmar temperature, and blood flow. We concluded that the hemodynamic changes during a thoracoscopic thoracic sympathicotomy seems to be the peripheral vasodilatation.