This study was conducted to assess the optimum period for Kirschner wire fixation and cast immobilization for displaced lateral condylar fracture of the humerus in children. We retrospectively reviewed 12 patients with displaced lateral condyle humerus fracture, ranging in age from 3-9 y, with injuries that occurred between Jan 2005 and Dec 2006. All patients were treated with two Kirschner wire fixation and elbow immobilization. In all except 2 patients, the Kirschner wires were maintained for 3 to 4 weeks. Mean time for union was 3.78 weeks and mean humeroulnar arch motion at last review was 138.7 degrees. Only one patient had a 5 degree increased carrying angle in valgus as compared to the non-injured side, and 50% had prominent scars > 4mm. We conclude that fracture union can be expected within three to four weeks for most children after open reduction and fixation with 2 Kirschner wires.