Background and aim of the work: Palmar Hyperhidrosis is an excessive and unpleasant sweating and it is under control of the thoracic sympathetic chain. At present, endoscopic upper thoracic Sympathectomy (ETS) offers a safe and durable solution of the condition. The operation includes excision, electro diathermy ablation or application of surgical clips on the thoracic sympathetic ganglia T2 and T3. The present study was done to compare the results achieved by excision and electro-diathermy ablation. Patients and methods: This prospective randomized study was conducted in King Abdul Aziz Specialist Hospital and Al-Hada Armed Forces Hospital, Taif- Saudi Arabia, from January 2007 to August 2010 and included sixteen patients with primary palmar hyperhidrosis. They were randomized into 2 groups; each of 8 patients. In one group; the sympathetic chains with T2 and T3 ganglia were excised on both sides and in the other group, the sympathetic chains and ganglia were ablated bilaterally using electro-coagulation diathermy hook. Results: There were 10 women and six men. The mean age of the ablation group was 23.6±7.6 years and in the resection group it was 22.5±8.4years. The mean operating time for bilateral Sympathectomy in the resection group was 74±18.6minutes; whilst in the thermal ablation group it was 32±7.8 minutes. The mean postoperative hospital stay in the excision group was 48±12 hours and in the ablation group, it was24±6 hours. No deaths occurred and all patients are discharged with dry hands. The mean follow up was 24±18 months. Intraoperative intercostal venous bleeding occurred in 18.75% of sympathectomies in the excision group but not in the ablation group. Neuralgic pain of the chest wall developed in 31.25% of sympathectomies of the excision group and 6.25% of the sympathectomies of the ablation group. Horner's syndrome developed in 6.25% per cent of the sympathectomies in both groups. Compensatory hyperhidrosis of trunk and thighs occurred in 37.5% of both groups. Recurrence developed in 6.25% of ablation group but no recurrence in the excision group. Conclusion: The rate of recurrence after endoscopic thoracic sympathectomy for treatment of primary palmar hyperhydrosis, if ablation is used, may be higher than resection, however; it is practically accepted as the procedure is easier, has shorter operating time with less liability to develop neuralgic pain and intercostal venous bleeding.