The prevalence of nosocomial infections in Scandinavian hospitals ranges between 8% and 11%. There are no continuous nationwide surveillance systems covering all types of nosocomial infections. Existing programs are limited to representative selections of patients, procedures, services, and hospitals. So far, interest has focused on surveillance and intervention in specific problem areas, e.g., intensive care units, surgical suites, and burn units; in use of antibiotics for prophylaxis in orthopedic and colon surgery; and in prevention of infections due to hepatitis B virus.Studies have shown that many traditionally used procedures can be omitted without any demonstrable influence on the rate of nosocomial infection. Generally, these investigations have led to the establishment of simpler and less expensive procedures. However, the results have suggested that physical containment is important to prevent the spread of certain types of nosocomial infections, e.g., those due to Staphylococcus aureus. Outbreaks dur to a common source of infection, such as those caused by Pseudomonas species, still occur in spite of the awareness of the risk. For the future, the most important trend seems to be toward intervention in medical procedures associated with a high risk of endogenous infection.