Lumbar Sympathectomy is a surgery for plantar hyperhidrosis, vascular and other reflex sympathetic diseases and has a various indications and physiologic effects. However it is not performed actively compared to thoracic sympathectomy because of its invasiveness. Therefore, we tried to perform lumbar sympathectomy using mediastinoscopy with small incision and introduce this new surgical technique. Material and Method: From July 2003 to December 2004, 18 patients undewent lumbar sympathectomy with mediastinoscopy at Inje University Sanggye Paik Hospital. There were 12 males and 6 females whose mean age was 24.3$pm$8.2 years ranging from 18 to 67 30 cases of lumbar sympathectomy was performed with mediastinoscopy of which 24 cases were for plantar hyperhidrosis and 6 cases for other diseases. Result: Mean operation time was 37.2$pm$12.5 minutes and mean post operation hospital stay was 3.1$pm$2.2 days. There was one post sympathetic neuralgia and one peritoneal opening. Conclusion: Lumbar sympathectomy using mediastinoscopy is a simple and effective technique and has the advantage of cosmetics, post operative pain and hospital stay. However, further studies with large number of cases should be carried out for better outcome.