There is a wide range of possible causes in chronic diarrhea. An attempt to correlate the symptoms with some clinically defined main categories facilitates a straight forward diagnostic approach. First and most important is a careful patient history. Very useful is a stratification regarding presence or absence of macroscopic lesions in the distal intestinal tract, usually done by coloscopy. Considering these principles, an overview of the most important causes for chronic diarrhea is given. Some relevant aspects of inflammatory bowel disease are discussed with special emphasis on the medical treatment. The major advantage of the newer 5-ASA compounds compared with sulfasalazine is the lower rate of side effects. 5-ASA enemas are very effective in the treatment of distal ulcerative colitis. Systemic treatment with corticosteroids is mandatory in severe case of ulcerative colitis and Crohn's disease.