Nonunion is extremely rare in children, Weber et al. concluded that considerable skill is required to induce nonunion in a child and its occurrence always results from a serious error in management. Twenty-six cases of delayed union and nonunion examined and treated at department of Orthopedic Surgery, Yonsei University, Wonju College of Medicine during the period of 1970 to 1988 was observed and analysed. 1. Of the 26 cases, there was 18 male and 8 female patients. The results showed more predominence of male over female patients. 2. Delayed union and nonunions commonly occurred over 5 year of age. 3. The causes of the fractures consisted of 12 Fell from heights, 5 Traffic accidents and others. 4. Of the 26 cases, there were 21 closed fractures and 5 open fractures. 5. Prior to admission to this hospital, 15 were treated conservatively and 10 treated operatively, and one received no treatment at all. 6. The sites of delayed union and nonunion were 10 phalanges, 6 tibia, and 3 ulna in order. 7. Probably causes of the delayed union and nonunion were unsatisfactory immobilization in 13 cases, infections in 6 cases, operative complications in 6 cases, interposition of the soft tissues in 2 cases in 2 cases, persistent seperation of the fragments in 1 case. 8. We are considered that the treatment of the nonunion must be individualizd but usually requires eradication of any infection, excision of the intervening fibrous tissue, bone grafting, and internal fixation.