Active immunisation against infections caused by hepatitis A virus. The vaccine is particularly indicated for those at increased risk of infection or transmission. For example immunisation should be considered for the following risk groups: Travellers visiting areas of medium or high endemicity, i.e. anywhere outside northern or western Europe, Australia, North America and New Zealand. Military and diplomatic personnel. Persons for whom Hepatitis A is an occupational hazard or for whom there is an increased risk of transmission. These include employees in day care centres, nursing, medical and paramedical personnel in hospitals and institutions, especially gastroenterology and paediatric units, sewage workers and food packagers or handlers. Haemophiliacs. Intravenouse drug abusers. Homosexual men. Patients with chronic liver disease (including alcoholic cirrhosis, chronic hepatitis B, chronic hepatitis C, autoimmune hepatitis, primary biliary cirrhosis). Since virus shedding from infected persons may occur for a prolonged period, active immunisation of close contacts may be considered. In addition there may be other groups at risk or specific circumstances such as an outbreak of hepatitis A infection when immunisation should be given.