A study was carried out by means of bacterial culture in 105 cases of open fractures at the Department of Orthopedic Surgery, National Medical Center from March 1989 to Febraury 1991. The results were as follows, 1. Micro-organism were isolated from 60 of the 105 cases in initial culture at emergency room, therefore the rate of contamination was 57.1%. The organism were Staphylococccus, Pseudomonas and Acinetobacter in order of frequency. 2. The 23 cases subsequently developed wound infection, the rate of infection was 21.9%. Of those 45 cases whose initial culture was negative, 6 cases developed late infection, therefore the rate of overall hospital infection was 7.6%. The organism were Pseudomonas, Staphylococcus and Enterobacter in order of frequency. 3. The contamination rate of type I fracture by Gustilo classification was 37%,,and that of type II and type III was 48%, 63%. 4. The average time from injury to debridement was 7.2 hours, there was no significant correlation between the infection rate and time from injury to debridement. 5. The rate of contamination classified by cause of open fracture was as follows:Explosive injury 66.7%, Industrial accident 58.9%, Traffic accident 55.0%, and others 37.5%.