Objective To analyze the treatment of old united lateral condyle fractures of humerus in children.Methods From January 1997 toFebruary 2002, 13 cases of old united lateral condyle fractures of humerus were treated. There were 11 boys and 2 girls. Their age was from 4 to 11 years(7.2 years on average). The primary diagnosis results were 4 cases of degree Ⅰ fracture, 5 cases of degree Ⅱ fracture and 4 indefinitely diagnosed cases. Elbow extension disorder occurred in 13 cases, which was limited 30-70°. The elbow flexion was limited morethan 90°. X-ray films showed 10 nonunion and 3 malunion of fracture. The timefrominjury to operation was 32 to 81 days (56 days on average) in 12 cases and6 months in 1 case. All cases were treated by open reduction and internal fixation. One case was treated combined with implanting bone. Results After a follow-up of 3 to 8 years(5.4 years on average), no cubitus varus or valgus occurred.Five cases had growth disturbances of the lateral condyle of the distal humerus. The movement of these elbow joints improved from 40° to 70° (56° on average). The time of clinical bone union was 6 to 8 weeks and no nonunion and delayed union were observed in X-ray films. Conclusion It is important to accurately diagnose for treatment of lateral condyle fractures of the humerus in children so as to reduce the occurrence of malunion of fracture. It can save the joint function and reduce the cosmetic deformity effectively to operate as earlyas possible.