The introduction to the West in the early 1980s of the Ilizarov circular external fixator and method resulted in rapid advances in limb lengthening, deformity correction, and segmental long-bone defect reconstruction. The mechanical features of and biologic response to using distraction osteogenesis with the circular external fixator are the unique aspects of Ilizarov's contribution. The most common indications for children and adolescents are limb lengthening and angular deformity correction. Surgical application and postoperative management of the device require diligent attention to detail by both patient and surgeon. Also required of the surgeon is a thorough appreciation of the basic principles of the apparatus, mechanical axial realignment, potential complications, and biologic response to stretching.