Clostridium difficile is an important pathogen, causing disease that ranges from mild self-limited diarrhea to life-threatening pseudomembranous colitis. It is estimated that C. difficile is responsible for 10% to 25% of all cases of antibiotic-associated diarrhea and for almost all cases of pseudomembranous colitis. C. difficile disease is mediated by two large toxins, A and B. The toxins damage intestinal epithelial cells and cause the clinical illness. Primary risk factors for C. difficile clinically apparent infection include antimicrobial therapy, hospitalization, residence in a long-term care facility, older age (≥ 65 years), and increased length of hospital stay. The incidence of CDI both in the hospital and the community is important in the understanding and characterization of the disease and its prevention. This observational, epidemiological study will advance the investigators understanding of CDI risk factors in several hospitals and possibly the community in the Asia Pacific region.