Fifty-seven cases of non-union examined and treated at Department of Orthopedic Surgery, Seoul National University Hospital during the period of 1968 to 1979 were observed and analysed. The results were summarized as follows: 1. Of the 57 cases,there were 43 male and 14 female patients. This result showed marked predominence of male over female patients. 2. Non-unions most commonly occured between 21 and 40 of age. 3. The causes of the fractures consisted of 22 traffic accidents, 20 fallings, 7 machinery injuries, 6 direct blows, and 2 chronic osteomyelitis. 4. Of the 57 cases, there were 20 open fractures and 37 closed fractures. 5. The sites of nonunion were lower extremities in 41 cases and upper extremities in 16 cases. The femur, 31 cases, was most commonly involved. 6. The mean duration from fracture to diagnosis of non-union was 14.8 months. 7. Prior to admission to this hospital, one received no treatment at all, 23 were treated conservatively, and the remaining 33 treated operatively. 8. Probable causes of the nonunions were unsatisfactory immobilization in 26 cases, operative complications in-24, infections in 3, interpositions of the soft tissues in 3, and separations of fragments in 1. 9. All patients received surgical operations, which were successful in 87.7%.