The pathophysiology and treatment of colonic motility disorders are reviewed. Colonic dysfunction is a common reason for patients to seek medical care, although patients' perceptions may not reflect abnormal function. Abnormalities in colonic function can result from a primary disorder of the large intestine or from metabolic, neurologic, collagen vascular, neoplastic, or infectious diseases. Irritable bowel syndrome, a common disorder of colonic motility, can be caused by alterations in colonic neuromuscular functions, afferent neural function, or psychosocial factors. Colonic dysmotility can also result from malabsorption of carbohydrates. The most severe form of altered colonic motility is acute colonic pseudo-obstruction. Diagnostic studies should be limited to tests appropriate for the patient's symptoms and apparent severity of disease. Most motility disorders are functional disorders and do not result in abnormal studies. Pharmacotherapy should be directed by objective measures, the most useful of which are measurement of whole gut transit time and quantification of the water content of stools. Treatment should be determined by the nature of the disorder and the symptoms involved. For constipation, treatment should begin with changes in diet, fluid and fiber intake, and concurrent medications. Irritant laxatives can have damaging effects and should not be used habitually; however, polyethylene glycol-based purgatives can be helpful. Newer prokinetic agents, such as cisapride, have been shown to promote colonic motility. For selected patients with intractable constipation, surgery has a good success rate. For patients with functional diarrhea, opioid analogues can increase fluid absorption and delay transit.