Subluxation and luxation of the ulnar nerve are normally congenital and can result in not only an irritation of the nerve but also sensory loss and motor weakness. The structures overlying the ulnar groove are responsible for the extent of nerve dislocation. In the case of subluxation, the ulnar nerve is compressed near the medial epicondyle by the edge of the ligamentous or muscular roof of the ulnar groove. In the case of luxation, ulnar nerve compression is located more distally under the aponeurotic arch of the M. flexor carpi ulnaris. We, therefore, distinguish between a proximal and a distal mechanism of nerve compression. In the years from 1970 to 1984 216 ulnar nerve compression syndromes in the elbow area have been treated and 208 cases have been evaluated. The authors found 77 proximal mechanisms (37%) and 54 distal mechanisms (26%). In 43 cases the proximal pressure was due to the ligamentum epitrochleo-anconaeum (20.7%) and in 34 cases to the epitrochleo-anconeal muscle.