More than 40,000 Norwegian troops have served in various UN peacekeeping operations since 1947. Coming from an area with low natural protection against hepatitis A, this disease has been a major concern to military authorities planning peacekeeping operations. More than 50 individuals have been repatriated due to hepatitis A, causing additional cost to the operations. After introduction of standard passive immunization with 2 ml immune globulins, reasonable protection was obtained for a limited time despite increasing risk of infection.