It is often difficult to achieve bony union and eradicate infection in treating infected non-unions of the fractured long bones. Authors carried out a clinical analysis of the 35 infected non-union cases, all aged 21 years or older, treated and followed for 6 months to 6 years from July 1979 to July 1988 in order to determine the possible factors which might influence the time required for attaining union. The results were as follows: l. In 22 of the 35 infected non-unions, the primary fracture site was open (62.9%). The remaining 13 cases (37.1% ) were the closed fractures associated with postoperative infection. 2. The sites of infected non-union were tibia in 19 (54.3%), femur in 13 (37.1%), and upper extremity in 3 (8.6%) cases. Tibia was more often involved in open fractures (63.6%). Femur, on the other hand, was more involved in closed fractures (61.5%). 3. After an average of 3.3 times of bony procedures, primary fixation was left in place in 15 (42.9%), external fixation was required in 11 (31.4%), and internal fixation was performed in 9 (25.7%). Bone graft was performed in 26 cases (74.3%). 4. Time required for achieving union was 7.1 month with stable primary fixation and 21.7 months with unstable primary fixation. Femur and tibia united at 10.5 (mean; ranged from 4 to 29) and 7.0 (mean; ranged from 3 to 19) months, respectively. 5. Bony union was delayed as the number of prior surgical procedures before successful treatment increased; the time for union was significantly shorter when either stable primary fixation or external fixation was combined with bone grafting. 6. Firmer bony union was achieved after performing Osteoperiosteal decortication with autogenous cancellous bone graft even in the presence of remaining infection at the non-union site.