Twenty eight long bone defects were treated with internal bone transport using Ilizarov method. The causes of defect were open fracture (ten cases), infected non-union(nine cases), and osteomyelitis(nine cases). The mean bone defect was 8.5cm ranging from 2.5cm to 22cm in open fracture and 5.8cm ranging from 1.8cm to 17cm in an infected nonunion, and 7.2cm ranging from 3.4cm to 12cm in osteomyelitis. Internal bone transport was performed with transverse ring system. Free latissimus dorsi muscle flap was done in three cases and rotational muscle flap in seven cases. Single level lengthening was done in 26 cases and double level lengthening in two cases. Fibular transport was done in five cases. All cases obtained bone union. The radiologic consolidation index was 89 day/cm in tibia, 71d ay/cm in femer, and 42.5 day/cm in humerus. External fixation index was 96 day/cm in tibia, 86 day/cm in femur, and 48.5 day/cm in humerus. Complications were pin tract infection(25 cases), equinus contracture of ankle(7 cases), knee flexion contracture(4 cases), delayed union(11 cases), premature consolidation(2 cases) and refracture(1 case). Ilizarov method is a useful treatment for large bone defect inopen fracture and infected nonunion. To obtain better result, careful postoperative management and intensive physiotherapy are recommended.