The effect of peripheral sympathetic block on the autonomic nerve function of the heart was studied using the head-up tilt test (HUTT) and right stellate ganglion block (RSGB). Blood pressure (BP), heart rate (HR) and the parameters of power spectral analysis of HR variability recorded during the HUTT were measured in 8 patients with chronic pain syndrome before and after RSGB. In the control state, the mean HR and the LF/HF component recorded during HUTT significantly increased whereas the HF component markedly decreased. Conversely, the mean HR and LF/HF and HF components during HUTT did not significantly alter after the RSGB procedure. There were no significant differences between the BP values before and after RSGB. These results suggest that RSGB suppresses cardiac sympathetic function without significantly affecting BP and thus may be a safe and effective therapy for the chronic pain syndrome.