This two-volume treatise, the collected effort of more than 50 authors, represents the first comprehensive survey of the chemistry and biology of the set of molecules known as peptide growth factors. Although there have been many symposia on this topic, and numerous publications of reviews dealing with selected subsets of growth factors, the entired field has never been covered in a single treatise. It is essential to do this at the present time, as the number of journal articles on peptide growth factors now makes it almost im­ anyone person to stay informed on this subject by reading the possible for At the same time it is becoming increasingly apparent that primary literature. these substances are of universal importance in biology and medicine and that the original classification of these molecules, based on the laboratory setting of their discovery, as "growth factors," "lymphokines," "cytokines," or "colony-stimulating factors," was quite artifactual; they are in fact the basis of a common language for intercellular communication. As a set they affect es­ sentially every cell in the body, and in this regard they provide the basis to develop a unified science of cell biology, germane to all of biomedical research.