The specific organ system effects of cancer and its treatment have been reviewed from the standpoint of nutritional impact. Nutritional impairment may occur as the result of specific organ system malfunction, and malnutrition itself may impair organ system functions in such a way as to compound these deficits. Nonmalignant, acute, and chronic illnesses resemble cancer in many ways, particularly in their ability to produce malnutrition and these organ system malfunctions. It is apparent that there is nothing particularly unique about many of these cancer states, from the standpoint of nutritional deficiency, that is not found in nonneoplastic conditions.