Fractures of the shaft of the radius and ulna occur commonly in children and are usually treated by closed reduction and plaster cast immobilization. Anatomic reduction is seldom necessary because of the remodelling potential in the child under 10 years of age, whereas the bones of children older than 10 years of age have less capacity to remodel and the diaphyseal fracture is unstable. In case of either unacceptable reduction or unstable fractures in adolescent patients, an operative treatment is required. In five children older than 12 years of age for whom conservative treatment had hailed, we treated a closed intramedullary nailing using a distal radial and proximal ulnar approach, and followed up for 1 year or more. All fractures healed within 6 weeks. No nonunion, cross-union or refrature occured. Another advantages of this method are negliable cosmestic defect and easy removal of the internal fixation device under local anesthesia. We think that closed intramedullary nailing with rush pin is a safe and reliable method to treat unstable forearm fracture in children older than 12 years of age.