Although virology and immunology are now considered separate disciplines, history shows that these areas ofinvestigation always overlapped and one cannot really exist without the other. This trend has become particularly significant and fruitful in the past few years in the area of herpesvirus research. The genomes of the most important herpesviruses have been sequenced, a significant portion of their genes have been identified, and many secrets of regulation of gene expr- sion have been unraveled. Now this progress sets the stage for a true revolution in herpesvirus research: analysis of interactions between the host and the virus. Because herpesviruses can induce, suppress, and fool the immune system, the most productive herpesvirologists are also expert immunologists, and the current results ofthis interdisciplinary effort are truly remarkable. Because herpesviruses cause many important human diseases, the devel- ment of vaccines against these agents is a very significant goal. This effort is also very challenging because of the complexity of herpesviruses and the lack of sufficient information about immune responses. The remarkable ability of herpesviruses to escape immune responses is - other feature that brings immunology and virology together. Herpesviruses - code many proteins that interact with and down-regulate some key elements of the immune system. Thisproperty of herpesviruses represents amajor challenge in developing strategies against these viruses. On the positive side, these viral proteins also provide novel tools for analyzing specific immune reactions and molecular mechanisms.