Objective To evaluate the surgical method and the results of endoscopic decompression and anterior transposition of the ulnar nerve for treatment of cubital tunnel syndrome. Methods Between May 2008 and August 2009, 13 cases of cubital tunnel syndrome were treated with endoscopic decompression and anterior transposition of the ulnar nerve. There were 4 males and 9 females with an average age of 47.5 years (range, 32-60 years). The injury was caused by fractures of the humeral medial condyle in 1 case, by long working in elbow flexion position with no obvious injury in 10 cases, and subluxafion of ulnar nerve in 2 cases. The locations were the left side in 6 cases and the right side in 7 cases. The disease duration was 4-30 months. The time from onset to operation was 3-20 months (mean, 8.5 months). Ten patients compl icated by intrinsic muscle atrophy. Results The operation was successfully performed in 13 cases, and the operation time was 45-60 minutes. All the wounds gained primary heal ing. All patients were followed up 12-18 months (mean, 14 months). The numbness of ring finger, l ittle finger, and the ulnar side of hand were decreased obviously on the first day after operation. The examination of electromyogram showed that the ulnar nerve conduction increased at 2 weeks, the ampl itude was improved, and recruitment of the intrinsic muscles of hand enhanced. In 10 cases compl icated by intrinsic muscle atrophy, myodynamia was recovered to the normal in 7 cases and was mostly recovered in 3 cases at 3 months after operation. The symptom of cubital tunnel syndrome disappeared and gained a normal function at 12 months after operation. According to the assessment of Chinese Medical Association and Lascar et al. grading criteria, the cl inical results were excellent in 10 cases and good in 3; the excellent and good rate was 100%. Patients recovered to work 12-16 days (mean, 14 days) after operation. No recurrence occurred during followup. Conclusion The surgical method of endoscope and microscope assisted three small incisions for treatment cubital tunnel syndrome has less invasion with small incision and complete decompression. Patients can recover to work early. It is a convenient and efficient procedure for treating cubital tunnel syndrome.