Pioneering work on hepatitis B virus and hepatitis delta virus, and the discovery of hepatitis B-like virus in animals during the 1970’s has been followed, over the past ten years, by an explosion of interest in how these viruses replicate, maintain chronic infections, and cause liver disease and hepatocellular carcinoma. The purpose of this book is two-fold. First, the authors of each chapter provide a summary of their specialty that will not only serve as an introduction, but will also provide the newcomer to hepatitis B virology with up-to-date information and insights into the goals and accomplishments of each area of investigation. Second, since the diversification of interests and increased specialization of hepadnaviruses researchers has reached a level where it is no longer possible for any one individual to read all the primary literature, this book will help to refocus interest on what is, after all, the major objective: to understand and ultimately treat or prevent chronic liver disease and liver cancer. Accordingly, chapters are included which span a range of interests, from the management of hepatitis B patients to new approaches to antiviral therapy, from the role of hepadnavirus gene expression in DNA replication to the role of ribozymes in the delta virus life cycle, from liver cancer in naturally infected woodchucks to liver disease in HBV transgenic mice to the use of hepatitis virus vectors to treat inherited enzyme deficiencies.