Feeding rats a semipurified diet containing casein as a protein source results in severe gastrointestinal (GI) toxicity when the chemotherapeutic drug methotrexate (MTX) is given. However, when soy protein is used in place of casein, rats are completely protected from toxicity. The purpose of this study is to determine if spy protein is protective against cyclophosphamide (CY) and 5-fluorouracil (5-FU) toxicity in rats (Cyclophosphamide and 5-fluorouracil are chemotherapeutic drugs that cause severe side effects to the GI tract because of their effect on cell division). Should this be the case, other experiments will be designed using combinations of 5-FU, CY and MTX which is used more routinely in the clinical setting than single drug regimens. If soy proves to be protective in toxicity associated with chemotherapy, it could easily be incorporated into an enteral product and be tested in cancer patients to boost their nutrient intake. This soy product would help to maintain patients' adequate nutrition and, therefore, their nutritional status which has been shown to increase tolerance to chemotherapy. Further, if toxic side effects were minimized, it may be possible to increase doses of drugs and more effectively kill tumor cells.