Why another series on infectious disease? The question is a fair one in view of the proliferation of monographs, texts, and periodicals on the vast subject of infectious disease. The goal of this series is to provide an additional service to the clinician in the form of clinical information not usually assembled in one convenient volume. One type of monograph presented in this series will cover a specific infection, detailing microbiologic, research and clinical aspects. It is hoped that such a compilation will be helpful in both its thoroughness and breadth to the clinician interested in this particular problem. The other type of monograph that this series will provide will discuss a clinical presentation that comprises many possible specific etiologies. Volumes in the series will be multiauthored, giving us the opportunity to invite authorities in each specific area to contribute their expertise and experience. Regular revisions are planned so that each volume will remain as current as it is thorough. We hope that our goals are met and that the present series of mono­ graphs establishes its own identifiable and valuable niche in the growing compendium of resource material available to the clinician. Preface to the Second Edition Since the first edition of Infectious Mononucleosis was published, we have seen exciting advances in our understanding of this disease.