Although medication-induced colonotoxicity is uncommon, it is important that it be recognized, because the initial therapy for this condition is medication discontinuation. This review categorizes the association between the listed medications and colonotoxicity as "well-established" or "probable," according to the following criteria: number of clinical studies by independent clinical investigators, total number of reported cases, plausibility of an association based on experimental and pharmacologic studies, and validity of an association in each reported case. Medications associated with colonic ischemia include cocaine, ergotamine, estrogen, amphetamines, digitalis, methysergide, and vasopressin. Medications associated with colonic pseudoobstruction include narcotics, phenothiazines, vincristine, atropine or other anticholinergics, ganglionic blocking agents, and tricyclic antidepressants. Medications promoting infectious or necrotizing enterocolitis include numerous antibiotics associated with pseudomembranous colitis, deferoxamine associated with Yersinia enterocolitis, chemotherapy associated with neutropenic colitis, and hyperosmolar medications or formulas in infants. Medications associated with an allergic, inflammatory, or cytotoxic colitis include gold compounds, nonsteroidal antiinflammatory drugs, alpha-methyldopa, flucytosine, methotrexate, salicylates, and sulfasalazine. Potassium chloride, administered in slow-release wax matrices, can cause intestinal ulcers. Chronic cathartic use leads to colonic hypomotility and abdominal distention. Methysergide can cause a colonic stricture due to retroperitoneal fibrosis. Intrarectally administered compounds that have produced a toxic colitis include powerful acids, bases, and other corrosives. Enemas using hypertonic radiographic contrast agents have been associated with colitis in patients with colonic obstruction.