At the time of the first edition of Principles of Cancer Biotherapy in 1987, this book represented the first comprehensive textbook on biological therapy. In 1991, when the second edition was published, there was still some doubt on the part of many oncologists and cancer researchers as to the therapeutic value of these new approaches. By 2003 and the fourth edition, it was generally agreed that biopharmaceuticals were producing major opportunities for new cancer therapies. Cancer biotherapy has now truly matured into the fourth modality of cancer treatment. This fifth revised edition describes the tremendous progress that has been made in recent years using biologicals in cancer treatment. This book summarizes an evolving science and a rapidly changing medical practice in biotherapy. In this new millennium, it is now possible to envision a much more diversified system of cancer research and treatment that will afford greater opportunities for a patient’s personalized cancer treatment. This was first envisioned in the 1987 initial edition of this textbook and is now a “new” and popular approach to cancer treatment. Some forms of cancer biotherapy use the strategy of tumor stabilization and control through continued biological therapy, akin to the use of insulin in the treatment of diabetes. This textbook illustrates new methods of thinking and new strategies for control of cancer. It is always difficult to move from past dogma to future opportunity, but this fifth edition of Principles of Cancer Biotherapy illustrates why it is so important to the patients for researchers and clinicians to explore and quickly apply these new opportunities in cancer biotherapy.