Ilizarov device is a circular external skeletal fixator with crossed transfixation wires and connecting rods. Its stability depends on the tension in the wire and the spatial orientation of the fixator frame. It provides extreme versatility for correction of three dimensional complex deformities including angulation, rotation, shortening and translation. In an attempt to identify the various factors that contributed to the outcome and the complications of lengthening, we reviewed the first 19 cases of leg lengthening by the Ilizarov technique in 17 patients with leg length inequality or dwarfism. Simultaneous correction of the three dimensional deformities was also aimed at in 13 patients, and osteosynthesis of congenital pseudarthrosis of the tibia in 2 patients. Follow-up periods averaged 1.6 years, ranging from 1 year to 2.8 years. The results were summarized as follows : 1. The amount of lengthening averaged 5.2cm, ranging from 2.0cm to 9.8cm. 2. The percentage increase was 27%, ranging from 9% to 58%. 3. The average healing index (month/cm) was 1.3months/cm and it was higher in the groups that had premature consolidation, complete osteotomy, single level corticotomy and neurologic compromise as compared with the groups that had adequate corticotomy, double level corticotomy and no neurologic complication. 4. The desired lengthening was obtained in 14 cases. Simultaneous correction of the deformities and osteosynthesis for nonunion were also achieved satisfactorily during lengthening. 5. There were sixteen cases of problems (84%), which were pin tract inflammation (7 cases), Transient senrory change (3 cases), knee joint flexion contracture (2 cases), nut breakage (2 cases). There were thirteen cases of obstacles (68%), which were equinus deformity(5 cases), premature consolidation (3 cases), pathologic fracture (3 cases), and delayed consolidation (2 cases). There was only one ture complication case. In conclusion, the Ilizarov technique was very effective for leg lengthening in children, particularly when three dimensional deformities were combined with leg length shortening. But a thorough knowledge of the Ilizarov technique and meticulous care during lengthening are mandatory to prevent the pitfalls and complications.