When cancer of the gastrointestinal tract is suspected, thorough studies should be made to determine the presence, type, and severity of the primary tumor and whether it has spread. Besides routine x-ray studies, angiography, scanning, and sonography may furnish valuable information. Endoscopy, which has revolutionized diagnosis of these tumors, not only makes it possible to obtain a specimen for histologic analysis without laparotomy but also reveals gross involvement as a guide to surgery. Staging of the lesion helps the physician select which patients would benefit from surgery and which instead should be treated with palliative chemotherapy or irradiation, or both. The patient's quality of life during treatment also must be considered. The side effects of multiple-agent chemotherapy, for example, may take too great a toll on the patient's ability to function. Continuous, long-term follow-up is essential. Metastases may develop after three to five years in particularly indolent tumors, and new primary lesions are far from rare.