To determine whether anatomical modification of sympathectomy diminishes severe postoperative compensatory hyperhidrosis.From January 1, 2000, to June 1, 2001, we prospectively studied 10 consecutive patients with primary palmar hyperhidrosis, aged 14 to 42 years. Medical therapy had failed in all patients. A preoperative and postoperative evaluation and thermoregulatory sweat testing were conducted in all patients. All patients underwent sympathotomy (bilateral simple disconnection) of the second thoracic ganglion input into the brachial plexus, and no sympathetic ganglia were violated.In the 10 patients, all 20 upper extremities improved postoperatively: 11 (55%) had near-complete cessation of palmar sweating, 8 (40%) had marked reduction in sweating, and 1 (5%) had delayed onset but full sweating at the end of the thermoregulatory sweat test. No intraoperative complications of hemopneumothorax or Horner syndrome occurred. Importantly, there were no moderate or severe postoperative hyperhidrosis complications.Sympathotomy to disconnect T2 ganglion input into the brachial plexus produces excellent results in the treatment of primary palmar hyperhidrosis and may lower the severity of postoperative compensatory hyperhidrosis complications. Long-term durability of the procedure requires further follow-up.