AbstractThe incidence of infection for clean surgical procedures should be less than 2%. The majority of infections are exogenous fromStaphylococcus aureus.These exogenous sources of bacteria include the ward, the theater environment, medical personnel, bed linen, and other infected patients. Endogenous infections may arise from the patient's own nose and skin; and although the majority of bacteria are staphylococcal, gram‐negative intestinal bacteria may colonize the skin around the perineum and are, therefore, important pathogens in hip replacement and aortobifemoral grafts. Methods of reducing exogenous infection include theater discipline, ultra clean air, surgical scrub, and isolating infected patients on the ward. Endogenous infections may be minimized by avoiding prolonged preoperative hospital stay, careful shaving only around the incision, and skin preparation with iodophors or chlorhexidine in alcohol. There is no place for antibiotic prophylaxis in clean surgical operations, provided the patient has a normal defense mechanism and provided a foreign body is not being implanted into bone or the circulation. Because of the morbidity and potential mortality of infected implants, antibiotics should be used in clean prosthetic surgery.