The Norwegian Institute of Public Health initiated a national surveillance system for nosocomial infections in 2002. The system is based on two annual one-day prevalence surveys recording the four most common types of nosocomial infection: urinary tract infections; lower respiratory tract infections; surgical site infections and septicaemia. All acute care hospitals in Norway (N=76) were invited to participate in the four surveys in 2002 and 2003. The total prevalence of the four recorded nosocomial infections varied between 5.1% and 5.4% in the four surveys. In all surveys, nosocomial infections were located most frequently in the urinary tract (34%), followed by the lower respiratory tract (29%), surgical sites (28%) and septicaemia (8%). The prevalence surveys give a brief overview of the burden and distribution of nosocomial infections. The results can be used to prioritize further infection control measures and more detailed incidence surveillance of nosocomial infections.