Clostridium difficile infection is responsible for approximately 3 million cases of diarrhea and colitis annually in the United States. The mortality rate is 1 to 2.5 percent. Early diagnosis and prompt aggressive treatment are critical in managing C. difficile-associated diarrhea. Major predisposing factors for symptomatic C. difficile colitis include antibiotic therapy; advanced age; multiple, severe underlying diseases; and a faulty immune response to C. difficile toxins. The most common confirmatory study is an enzyme immunoassay for C. difficile toxins A and B. The test is easy to perform, and results are available in two to four hours. Specificity of the assay is high (93 to 100 percent), but sensitivity ranges from 63 to 99 percent. In severe cases, flexible sigmoidoscopy can provide an immediate diagnosis. Treatment of C. difficile-associated diarrhea includes discontinuation of the precipitating antibiotic (if possible) and the administration of metronidazole or vancomycin. Preventive measures include the judicious use of antibiotics, thorough hand washing between patient contacts, use of precautions when handling an infected patient or items in the patient's immediate environment, proper disinfection of objects, education of staff members, and isolation of the patient.