This series of books attempts to present, in a comprehensive manner, the field of oncology divided into three major areas; etiology, biology, and therapy. These books should serve as landmarks in the rapidly expanding experimental and clinical "universe" of this field. To some, they will be introductory; to others, a summary; for all, critical comments on the futuI'e of research. In l'ecognition of the difficulties inherent in attempting to pause and reflect while experimental data emerge with ever-increasing rapidity, the presentations take the form of overviews rather than reviews. Where possible, an historical perspective on observations and experimentation which led to our present understanding is presented, the state of the art in technique and approach is reviewed, and the gaps in knowledge and in technique are indicated. The aim throughout is integration-using the findings from one approach for comparison with others. The tremendous expansion of interest in oncology as a medical-biological discipline stimulated the publication of these volumes. This expansion, well warranted in terms of the impact of oncology on human morbidity, has been characterized by at least three phenomena. First, there has been an enormous increase in money and manpower devoted to the investigation and treatment of malignancy. That the research has become more and more "directed" or program-oriented signals the interest of those beyond the scientific community in the management of the eHort. Second, increasing numbers of students are entering the field of oncology as their major training program.