Acute viral hepatitis is one of the most prevalent infectious diseases in Hong Kong and hepatitis A accounts for two thirds or more of reported cases. Improved sanitation has led to a decline in hepatitis A infection in childhood but more clinically overt adult cases now occur. Shellfish ingestion and recent travel are important risk factors. A highly immunogenic and effective inactivated hepatitis A vaccine is available. Hepatitis E is of emerging importance as a cause of acute hepatitis. Large outbreaks have occurred in China and other developing countries; sporadic cases occur in Hong Kong. High mortality is associated with hepatitis E complicating late pregnancy. Serological diagnosis by enzyme immunoassay for anti-HEV is available. The education of travellers to endemic areas is advised with special caution being given to pregnant women. A vaccine for hepatitis E is not yet available.