Operative treatment for closed fractures of the long bone has many advantages including early restoration of function by stable fixation, but has untoward problems including postoperative infection. The authors reviewed 19 cases of postoperative infection for closed long bone fracture during the period from January, 1990 to December, 1995 and analyzed about clinical, radiologic, pathologic findings and found causes of infection. Most cases were associated with multiple fractures of major bones or injuries to the vital organs and delayed over 48 hours after injury to operation. Operation time was prolonged due to the simultaneous operations for multiple fractures and associated open fractures at the same time. Staphylococcus aureus was the most frequent offending organism. Irregular resorption of plate-bone interface with resultant gap between the plate and bone, on the radiographic follow up, may indicate postoperative infection.