We reviewed the results of treatment of forty open diaphyseal fractures of the lower extremity in thirty-five children. The patients were between three and sixteen years old, and they had been managed between 1980 and 1988. The minimum duration of follow-up was one year. Eighty-six per cent of the patients had been injured in a motor-vehicle accident, and 74 per cent had associated injuries. Thirty-one of the fractures were Grade-II open or Grade-III open and seven were Grade-I open, according to the classification of Gustilo and Anderson. Two patients who had initially had a closed fracture were treated with a fasciotomy for a compartment syndrome, so these two fractures were included as open. Four other patients who had a Grade-II or III open fracture also needed a fasciotomy. All wounds were treated with immediate and repeat debridement and early soft-tissue coverage. Twenty-two fractures healed primarily. There were three early amputations. Twelve fractures that healed after six months were classified as delayed unions and three fractures were classified as non-unions because of the absence or arrest of healing, as seen on serial roentgenograms. Additional intervention was used to achieve union of eight of the fifteen fractures that had been classified as a delayed union or a non-union. Ten of the forty fractures were associated with infection, but osteomyelitis developed in only one patient. No patient had a growth arrest. Only one patient had a limb-length discrepancy that was more than two centimeters. Three early amputations and one delayed amputation were performed in patients who had a Grade-IIIC open fracture.