With the advent of transthoracic video-assisted endoscopic electrocautery of the second and the third sympathetic ganglia for the treatment of palmar hyperhidrosis, it is possible to approach the stellate ganglia with ease. To see whether stimulation of stellate ganglia in humans is similar to the case in dogs, we stimulated the sympathetic ganglia in 18 palmar hyperhidrosis patients with a coagulation power of 5 W at a frequency of three times every 2 s. We found that left stellate stimulation prolongs the Q-T interval and increases the heart rate, whereas right stellate stimulation affects the Q-T interval and heart rate insignificantly, just like the case in dogs in which the left stellate ganglion predominates the right one in determining the Q-T interval. Left stellate stimulation after destruction of the left second and third ganglia also prolongs the Q-T interval, suggesting that the left stellate ganglion is more important in determining the Q-T interval.