The most important and relevant symptoms of colonic dysfunction are diarrhea, constipation, urgency, and pain. Despite the efforts of many investigators over several decades, the motor physiology of the human colon is still relatively obscure. In practice, measurements of transit are the best characterized and most widely available tests of colonic motor function. Colonic hypersensitivity, implying an abnormality of afferent signalling, is assuming greater importance in the pathophysiology of conditions as common as irritable bowel syndrome and inflammatory bowel disease.