Four cases of different distal ulnar nerve lesions are presented. Compared with the median nerve in the carpal tunnel syndrome (CTS), the surgical procedure with the distal ulnar nerve has to be determined more by the location of the nerve lesion. Because of the small number of cases and the different types of lesion, pressure on the nerve in the "Loge de Guyon" cannot yet (in contrast to the CTS) be defined by intraoperative pressure recording. An extreme pressure elevation with active movements by the patient might point to a nerve entrapment syndrome. Compared with phalen's test in the carpal tunnel syndrome, and because of its low specificity abduction of digit 5 as a sensitive sign of sensory disturbances in the "Loge de Guyon" is unreliable.