Patients receiving antibiotics or having just completed a course of antibiotics should be observed for the development of diarrhea. The diagnosis of antibiotic-associated colitis can be made by careful proctoscopic examination. If colitis is found, the antibiotic should be discontinued, vigorous supportive therapy should be instituted, and the patient should be observed carefully. Following these guidelines, the prognosis for antibiotic-associated colitis should be favorable.