The frequency of nosocomial infection is increasing. The most common sites of such infection are the urinary tract, surgical wounds, the lower part of the respiratory tract, and the skin and subcutaneous tissues. Various techniques are available for prevention of nosocomial infections, but among the most important aspects are understanding and acceptance of responsibility by hospital personnel. The establishment of a surveillance system with a nurse epidemiologist to serve as liaison and educator among professional and ancillary groups within the hospital may be hard to justify on a cost basis to hospital administrators but is important in the control of nosocomial infections.