The authors have discovered that many cases of unexplained pain in the hand and upper extremity have the superficial palmar branch of the radial artery as either a cause or a conduit for the pain. The artery travels immediately radial to the flexor carpi radialis and enters the hand at the thenar eminence. It takes a variable course into the palm. The authors have ligated and resected a 1 cm segment of the artery in 5 patients to date and completely relieved pain in the thenar eminence in 2 patients, the median sensory dermatone of the hand in one patient, and the radial wrist in one patient. In 2 cases, intractable pain in the basal joint of the thumb with normal radiologic findings had previous temporary relief with joint space injections with seroid/anesthetic mixtures. They gained complete and permanent relief after the ligation and resection. A very interesting phenomenon has occured in 3 patients who had the procedure done with an IV regional block with 0.5% lidocaine. Although these patients were anesthetic in the hand during the procedure, they both exclaimed with sudden pain replicating their symptoms at the instant the vessel was ligated. They had no more pain after the vessel was transected. In one patient,chronic headache pain also suddenly ceased at the instant of ligation. All three patients spontaneously noted this vocally, but none of them were aware that the ligation was taking place at that time. The authors are presently screening patients with chronic pain in the radial aspect of the hand and upper extremity by giving them a test injection of 1 cc of a solution of equal parts 0.5% marcaine and 1% lidocaine immediately deep to the vessel at the level of the distal wrist crease. Prompt, significant improvement has been claimed by 5 of seven patients tested. All of the patients with positive response to the injection have had complete pain relief after surgery,with followup ranging from 2 months to 2 years. A dilated vessel was found in only 2 of the patients, but had otherwise normal pathology findings. The authors believe that the radial artery may be a conduit for sympathetic fibers that mediate pain. Ligation may be a new useful modality for treatment of enigmatic sympathetically mediated pain in the upper extremity. Further investigation is encouraged.