Thirty-five patients with tardy ulnar nerve palsy caused by cubitus valgus (33 cases0 and varus (2 cases) deformities were retrospectively studied. All patients had a history of old fracture on the distal humerus during childhood. The mean interval between the previous fractures and the onset of ulnar neuropathy was 19 years. The severity of nerve palsy was classified as McGowan's grade I in 24 patients, grade II in 8 patients, and grade III in 3 patients. The mean carrying angle was average 29 degrees in 33 cases with cubitus valgus and it was decreased to average 11 degrees postoperatively, but the angle was average -23 degrees preoperatively in 2 cases with cubitus varus and it was corrected to average 9 degrees postoperatively. the cause of palsy was analysed by mechanical stetching in 11 cases, compression by a fibrous band between the two heads of flexor carpi ulnaris in 8 cases, and diffuse fibrous adhesion around the ulnar tunnel in 5 cases. All patients was treated with supracondylar closing wedge osteotomy accompanied with anterior ulnar nerve transposition in 13 patients, corrective osteotomy only in 12 patients, and anterior ulnar nerve transposition only in 10 patients. Their end results were analysed as good in 24 cases, fair in 8 cases, and poor in 3 cases within average 6 months after the operations (4 to 13 months). The poor results was obtained in 3 cases out of 9 cases with corrective osteotomy group (33.3%). Conclusively, a tardy ulnar nerve palsy caused by post-traumatic elbow deformities should be corredcted with anterior ulnar nerve transposition with or without corrective closing wedge osteotomy but not by corrective osteotomy only, because of compressive neuropathy by diffuse fibrous adhesion or bands of two heads of FCU around the ulnar tunnel in elbow.