" . . . the motto for the therapeutics of the future will have to be de sedibus et causis pharmacorum. " P. EHRLICH, 1909 Exciting events in the basic disciplines of virology, immunology, and pharmacology continue to advance the understanding of the pathogenesis and control of virus diseases. At the same time, the rational development of antiviral agents is attracting, to an increasing extent, the interest of workers in other disciplines. Improvements in technology facilitate the definition of potential target sites for antiviral intervention and unmask new viral and host genes. The outcome is a further steady development of new antiviral agents which approach the "magic bullets" first proposed by PAUL EHRLICH. Remarkable advances in protein synthetic methods that yield polypeptides which inhibit active sites of viral proteins have aided substantially in the basic and clinical study of these antiviral agents. In addition, the extremely rapid progression in recombinant DNA techniques, leading to the synthesis of large quantities of gene products, is also increasing our opportunities at a dashing pace. New information and developing technology facilitate research on the mechanism of action, toxicity, pharmacokinetics, and pharmacodynamics of new agents. The list of clinically effective antiviral agents is expanding and the number of potentially useful compounds is growing rapidly. This book is a combined theoretical text and practical manual which, it is hoped, will be of use to all who have an interest in virus diseases, particularly scientists, physicians and graduate students.