Intraluminal agents include clays, activated charcoal, and cholestyramine these adsorbents and other binding resins can interfere with the absorption of orally administered antidiarrheals and other drugs and are unlikely candidates for use in most cases of diarrhea in cancer patients. Opiate agonists are the most commonly used intestinal transit inhibitors they can be effective in treating cancer treatment-related diarrheas but must be used cautiously. Antidiarrheal agents may be classified as intestinal transit inhibitors, intraluminal agents, proabsorptive agents, and antisecretory drugs. The general goal of antidiarrheal therapy is to reduce fluid loss in the stool by inhibiting intestinal secretion, promoting absorption, and decreasing intestinal motility. Diarrhea may be induced by chemotherapy, radiation therapy, surgery, graft-versus-hot disease (GVHD) or infection after bone marrow transplantation, and other causes. Diarrhea is common in cancer patients and may interfere with cancer treatment. The efficacy and use of antidiarrheal agents in patients who diarrhea associated with cancer treatments are reviewed.