The proximal ulnar compression syndrome when it is not a result of trauma, tumors, inflammatory and degenerative processes, inborn deformations or external pressure, is caused by two mechansims, namely the pinching of the ulnar nerve between the proximal edge of the ligamentous and muscular coverings of the cubital tunnel and of the exit of the nerve from the tunnel under the tendinous arch of the flexor carpi ulnaris. The compression itself is dependent upon the possibility of subluxation of the ulnar nerve. Therapy should consists not only in "decompression", but also in a simultaneous anterior transposition of the ulnar nerve.