Hepatitis B is a disease of the liver caused by the Hepatitis B virus (HBV), a member of the Hepadnavirus family and one of several unrelated viral species which cause viral hepatitis. It was originally known as "serum hepatitis" and has caused current epidemics in parts of Asia and Africa. Hepatitis B is recognised as endemic in China and various other parts of Asia. The proportion of the world's population currently infected with the virus is 3 to 6%, but up to a third have been exposed. Symptoms of the acute illness caused by the virus include liver inflammation, vomiting, jaundice, and rarely, death. Chronic hepatitis B may cause liver cirrhosis which may then lead to liver cancer. This book presents the latest advances in the field.