Clostridium difficile diarrhea is an expensive, life-threatening infection associated with serious morbidity and mortality, even among previously healthy individuals. Relapses from the infection are common following standard antibiotic treatments, with 3-5% of patients who contract C. difficile diarrhea unable to discontinue vancomycin due to continual relapses. Such patients may have a focal immunodeficiency in which they fail to mount an immune response against C. difficile. For these individuals, antimicrobial therapies are unable to eradicate the microorganism because no antibiotics are capable of killing C. difficile spores. Although they are considered alternative medicine, probiotics have provided a safe and effective means of restoring gastrointestinal flora and alleviating diarrhea, particularly for individuals experiencing multiple relapses.