Introduction & Objective: Anatomy of median nerve may be different in patients with carpal tunnel syndrome compared to normal persons. This study was performed to help to avoid injuring the median nerve during carpal tunnel release surgery.Materials & Methods: Forty patients with severe idiopathic carpal tunnel syndrome, who had undergone carpal tunnel release, were included in this study. The distance between distal wrist crease and the origin of recurrent branch of median nerve was determined. The anatomy of recurrent branch of median nerve was investigated to determine its status regarding extraligamentous, subligamentous or transligamentous patterns. The location of the origin of recurrent branch (ulnar, radial or palmar side) was also studied.Results: From these 40 patients, 38 were women and 2 were men. Their mean age was 54 (37-76) years.The anatomic pattern of recurrent branch was extraligamentous in 38 cases, subligamentous in one case and transligamentous in a single case. In all cases the origin of recurrent branch was from the radial side and we did not have any case of ulnar side or palmar side origin. The mean distance between distal wrist crease and the origin of recurrent branch was 31 (29-35) millimeter.Conclusions: According to these results there are differences in the anatomy of median nerve in patients with carpal tunnel syndrome with that of normal persons, and surgeons should pay attention to these findings during carpal tunnel release surgery.