In 1814, Monteggia first described a fracture of proximal third of the ulna with dislocation of radial head. And in 1967 Bado classified and included all fracture of ulna at any level with a dislocstion of radial head, under the name of Monteggia lesion. The authors reviewed ninty-eight Monteggia lesion that were treated at 25 Orthopaedic institutes over 10 years period (1981 through 1990), with pariticular emphasis on the differences between child and adult, and between 2 period groups (Group I:1981-1985, Group II:1986-1990). The results were as follows. 1. Total 98 patients were 32 children and 66 adults, and 29 Group I and 69 Group II. 2. The most common cause of injury was fall (88%) in children and traffic accident (53%) in adults. 3. According to Bado classification, type I was 53%, type II 9%, type III 38% in children, but, in adults, type I was 73%, type II 12%, type III 8% & type IV 8%. And in children, there were 9 equivalent lesions. 4. In locational incidence of ulnar fracture, metaphyseal level was most common in children, but junction of proximal & middle one-third level in adults. 5. Common treatment of ulnar fracture was closed reduction (59%) in children, and open reduction with internal fixation (97%) in adults. 6. Delay in diagnosis of dislocation of radial head was 22% in children, and 21% in adults. But in comparison between 2 period group, there were distinct differences as 34% in Group I and 16% in Group II. 7. The results (Bruce et al criteria) for the 38 patients followed 6 months and more were satisfactory in 80% of children and 67% of sdults, and satisfactory in 89% of Group I and 53% of Group II lesions. The poor results in Group II were caused by higher distribution of patients with soft tissue injury.