Since 1970 all postoperative bacteriological findings recorded in surgical patients have been analyzed and compared with the postoperative course. There are also regular checks of bacterial invasion in the operating suites and in the intensive care units. By such means as systems of double lock for personnel and equipment, regular surface disinfection, frequent hand disinfection, cleaning of the respirators with antiseptics, etc., the authors have been able to reduce the incidence of hospital infection very drastically. These measures also almost eliminated cross-infections in patients on long-term ventilation and complications with long-term indwelling catheters.