This study was undertaken to determine the etiology of surgical infections in Kuwait: the incidence, kinds of infections, types of microorganisms involved, and the pattern of mixed infections. Microorganisms were isolated in 320 infections; 180 single organisms, and 140 polymicrobial. Skin and biliary tract infections were caused largely by single organisms, while pelvic infections and intra-abdominal sepsis were predominantly polymicrobial. Aerobic bacteria were the major cause of infection in 162 (50.6%) patients, anaerobes in 57 (17.8%), and mixed in 101 (31.6%). Aerobic bacteria were predominant in skin and biliary tract infections, and infections following gynecological and miscellaneous surgery. Mixed infections were perianal, intra-abdominal sepsis, and infections following bowel surgery. The most common aerobes were Staphylococcus aureus and Escherichia coli and the most common anaerobes were the fragilis group of Bacteroides. The importance of identifying anaerobes in wound infections is stressed in order to choose those antimicrobial agents suitable for prophylaxis and treatment.