This preclinical research program is designed to: 1. Define the severity and time course of treatment (chemotherapy and/or radiotherapy) induced changes in animal weight, food and water intake, and gastrointestinal transit time. 2. Assess the extent to which the above factors contribute to the severity of acute gastrointestinal tissue toxicity (mainly, the proliferative response of the mucosa). 3. Attempt to ameliorate treatment associated gastrointestinal toxicity through nutritional modifications, such as treatment dose-time scheduling, and enteral nutrient administration. 4. Assess the effect of pretreatment nutritional status on the proliferative response of the gastrointestinal epithelium to therapy.