In the treatment of spinal disorder, the introduction of pedicle screw system is an innovation in modern spinal surgery. This kind of new instrumentation provides correction, adjustment, stabilization, firm fixation and short segment fusion. Everybody should know that these complexities of instrumentation will increase the rated of complications, especially postoperative infection. Postoperative infections continue to be a source of frustration for patients and surgeons, and can lead to significant postoperative difficulties. So we analysed the postoperative infection from the 284 cases we operated on during the September 19S8 to August 1992 and obtained following results: 1. There were 17 cases(6.0%) of postoperative infection. Among them Scases(2.8%) were deep infection. 2. Average fused segments were 3.64 and 2. 96 in deep infection and control group respectively. 3. Staphylococcus aureus was the most frequent organism. Other recurring organisms were St. epidermidis, Enterobacter cloacae and so on. Many patients had multiple organisms. 4. Most significant risk factors for postoperative infection were obestity and prolonged surgery. 5. Just preoperative prophylactic antibiotic administation is more valuable than no prophylaxis and too early administration. 6. Postoperative acute deep infection is is not as easily diagnosed. The clinical manifestation such as sudden increase in pain at the operative site is the most valuable sign. 7. Maintaining the instrumentation in place, continuous irrigation system and the appropriate parenteral antibiotics were the choice of treatment.