Gastrointestinal tract malignancies encompass a spectrum of diseases with marked differences in etiology, incidence, biological behavior, and treatment outcome. The incidence of new gastrointestinal cases recorded yearly for patients residing in the United States is approximately 230,000, representing nearly 20% of all cancer cases. Worldwide, gastrointestinal malignancies are responsible for the largest number of cancer deaths, particularly because of the high incidence of hepatocellular and gastric cancer in other countries. Gastrointestinal Oncology is directed to those most involved in the multidisciplinary approach to the gastrointestinal cancer patient, including medical, radiation and surgical oncologists; gastroenterologists; interventional radiologists; pathologists; oncology nurses; and oncology physicians-in-training.