This book is an update of Interferon, published in 1969 by Dr. Jan Vilcek. The field of interferon research has since expanded from its former narrow treatment of interferon strictly as an antiviral substance, such that The Interferon System now encompasses cellular modulations ranging from immune alterations to cell proliferative restrictions to antitumor activities. The steadily increasing number of these non-antiviral functions of interferons emphasizes the need for a comprehensive - and critical - review of the entire literature of interferon studies. The text, with its supporting bibliography, provides complete coverage of interferon research. A newcomer to the area should find here all the informa tion necessary to understand why interferon, which has been studied for more than twenty years and which originally stirred excitement over its clinical pros pects, is still inspiring speculation about this potential. For those already fa miliar with the seemingly perpetual clinical promise of interferon, this volume should serve as a valuable reference source, the largest bibliography on the subject ever to appear under one cover. Clearly, this book should be considered only as an introduction to the topic and as a reference source; most questions about the interferon system are still unanswered - even unasked. Hopefully this summation and critical evalua tion of work done to date will stimulate and facilitate further progress.