Under sponsorship of the National Institutes of Health of Japan, an international conference entitled "Immunity and Prevention of Herpes Zoster" was held in 1 Osaka, Japan, March 8-10, 1999. Attendees included basic and clinical investi gators from Asia, Europe, and North America. The meeting was organized to explore progress made in basic virology and molecular understanding of varicella zoster (VZV), and to provide information on current knowledge of latency of VZV in humans. Updates on the immunology responses of humans to VZV, and a description of the current status of varicella vaccine worldwide were also included. In addition, the possibility of prevent ing zoster in people latently infected with wild-type VZV by immunizing them with varicella vaccine was presented. The papers in this volume include written summaries of most of the presentations given at that conference. Coincidentally but appropriately, the conference marked the twenty-fifth or "silver anniversary" of the first publication of the development and use of live varicella vaccine to prevent varicella, by Takahashi and his colleagues. Because varicella vaccine is the first herpesvirus vaccine licensed in use for humans, it is of special interest to all individuals who studied these pathogens. In view of the interest in developing vaccines against other herpes viruses, there was also a presentation on the current status of vaccines against cytomegaloviruses (CMV) at the conference.