During the past decade there has been extraordinary progress toward the development of vaccines for the prevention of type A and type B hepatitis. The successful propagation of hepatitis A virus in cell culture in 1979 was followed by the preparation of experimental live attenuated hepatitis A vaccines that have been shown to induce antibody in marmosets and chimpanzees and protect immunized marmosets against challenge with hepatitis A virus. The first human immunization trials will begin in mid-1982. An inactivated hepatitis B vaccine that was licensed in the United States in November 1981 has been shown to be safe, immunogenic, and effective. When this vaccine becomes available for use in July 1982, it will be recommended for persons who are considered to be at increased risk of contracting hepatitis B infection. Future generations of hepatitis B vaccines may be prepared from hepatitis B surface antigen derived from DNA recombinant technology or by in vitro synthesis of HBs Ag determinants by chemical means.