This is a clinical practice guideline for adult cancer patients. The guideline provides recommendations for the diagnosis and treatment of non-infectious and infectious gastrointestinal complications often experienced by these patients. Specific conditions examined include paraneoplastic diarrhea, therapy-associated diarrhea, neutropenic enterocolitis, Clostridium difficile infection, other bacterial infections causing diarrhea (e.g. non-typhoidal Salmonella, Shigella, Yersinia, and Campylobacter spp.), viral infections, and parasitic infections.