Objectives: to review our total experience of thoracoscopic sympathetic trunk transection for the treatment of palmar hyperhidrosis and second and third thoracic sympathetic ganglionectomy for axillary hyperhidrosis. Design: longitudinal cohort study following up consecutive patients for 0.3 to 5.5 years. Subjects: fifty-four consecutive patients undergoing thoracoscopic sympathectomy for hyperhidrosis. Methods: prospective evaluation of immediate technical success, complications, late recurrence of hyperhidrosis and patient acceptability. Results: 100% initial cure for palmar hyperhidrosis, 91% of sympathetic ganglionectomies for axillary hyperhidrosis were technically successful and initially curative. Compensatory, sweating 44% patients, most severe after bilateral sympathetic ganglionectomy. Complications occurred in 14% patients, all resolving without further intervention. There were no cases of Horner's syndrome. 13% patients reported a return of some palmar sweating. 5.4% patients developed recurrent palmar hyperhidrosis at 6, 15 and 21 months postoperatively. Conclusion: transection of the sympathetic trunk between the first and second thoracic sympathetic ganglia initially curves 100% of patients treated primarily for palmar hyperhidrosis. Technically successful 2nd and 3rd thoracic sympathetic ganglionectomy initially cures 100% of patients with axillary hyperhidrosis. Compensatory sweating is common after bilateral sympathectomy, Recurrent palmar hyperhidrosis occurs in 5.4% of cases, but can be cured by a second thoracoscopic sympathectomy. Horner's syndrome is an avoidable complication of thoracoscopic sympathectomy.