The Ilizarov technique has been used successfully in the treatment of nonunion of long bone accompanied by infection, severe bone and soft tissue defects, and deformity. We report the results of treatment of 21 cases of nonunion using the Ilizarov technique. There were 20 males and 1 female with an average age of 34.2 years (range, 8-72 years). The average follow up period was 45 months (range, 12-74months). Infected nonunion(15/21 cases) was the most common cause of nonunion. The treatment methods include simple compression method(4 cases) and internal and external bone transport method(17 cases). Bony union was achieved in 20 cases out of 21 cases. One case is still having difficulty in achieving union. The mean time to union was 7.3 months in femurs and 6.3 months in tibias. The amount of bone defect that developed after the removal of infected bone fragments and soft tissue averaged 3.8cm (range, 2.3-9cm). The healing index, in cases of bone transport, was an average of 45 days per cm (range, 30-62 days per cm). Complications developed in 17 cases out of 21 cases. Pin site infection occurred in 5 cases, premature consolidation in ~1 case, angulation deformity in 2 cases, LOM of the knee in 2 cases, equinus deformity in 2 cases, ankle stiffness in 3 cases, and nonunion in 1 case. The Ilizarov technique is thought to be effective in the treatment of complicated nonunion combined with shortening, deformity, bone defect and infection. However, in order to reduce complications caused by the Ilizarov method, accurate surgical techniques and postoperative care are necessary.