'You damn sadist/said mr cummings 'you try to make people think. ' -Ezra Pound (Canto 89) What makes herpesviruses unique? It is certainly not the size of their genomes or the individual features of their reproductive cycle, although in toto striking features that are exclusive to the herpesviruses abound. Unquestionably, the pre-eminent feature is the relationship of herpes viruses with their natural hosts. As described in preceding volumes, all herpesviruses seem to be able to colonize and to remain in a latent, nonproductive form for life of their hosts. Once established in the host, the relationship is best described as that of an armed truce. What happens when this truce breaks down or when the host encounters the virus for the first time is the subject of this volume. We have focused primarily on the five human herpesviruses [herpes simplex virus 1 (HSV-l), herpes simplex virus 2 (HSV-2), cytomegalovirus (CMV), varicella zoster virus (VZV) and Epstein-Barr virus (EBV)] because much more is known about them than about any other herpesviruses, and because it is of interest to compare both the diversity of manifestations of infections with human herpesviruses and the spectrum of human responses to these viruses. This volume summarizes the current knowledge of the pathogenesis and immunobiology of herpesvirus infections in man and describes new and developing approaches to prophylaxis and treatment. It contains con tributions from distinguished research scientists presently engaged at the forefront of these scientific investigations.