Phantom sweating is a sensation in which the patient feels that sweat is about to burst out of skin pores, but in which sweating never actually occurs. In a series of 100 patients undergoing bilateral upper dorsal sympathectomy for palmar hyperhidrosis, 82 patients were specifically questioned and 48 (59%) reported phantom sweating. Phantom sweating started soon after the operation, was triggered by the same stimuli that caused hyperhidrosis preoperatively, lasted for a few seconds, and tended to diminish with time. In an average follow-up of 18 months, the phenomenon disappeared in 11I patients (23%). Phantom sweating is probably a symptom of residual sympathetic activity.