A Bacteriological study was carried out by means of bacterial culture and sensitivity test in 144 cases of fresh orthopedic wound seen at the Department of Orthopedic Surgery, Hanyang University Hospital from November 1973 until August 1974. The sensitivity test for various organisms which were isolated from the wounds was performed by Ericsson's method. The following conclusions were made. 1. Micro-organisms were isolated from 43 of the 144 cases, therefore the rate of infection in the fresh orthopedic wounds was 29.8%. 2. The order of frequency of isolated organisms was as follows: Staphylococcus albus 17 cases (39.5%), Alcaligenes faecalis 7 cases (16,3%), E. coli 5 cases (11.6 %). Mixed infection 5 cases (11.6%). Staphylococcus aureus 4 cases (9.3%). Pseudomonas aeruginosa 3 cases (7%). Aerobacter aerogenes 1 cases and B-hemolytic streptococcus 1 case. 3. The rate of wound infection classified by cause of wound was as follows: Explosive injury 66.7%. Traffic accident 31.4%. Industrial accident 28.1% and Others 23%. 4. The more severe the wound, the higher was the rate of wound infection. 5. The rate of wound Infection was increased in proportion to the time of exposure of the wound but time seemed to be less important then extent and severity of the wound. 6. The rate of hospital infections was 13.2%. The most common organism was pseudomonas aeruginosa (10 cases) and the next common organisms were E. coli (3 cases) and Alcaligenes faecalis (3 cases). The above mentioned 3 micro-organisms accounted for 84.2% of the hospital infections.