Background/Aims: As the incidence rate of and mortal-ity from pseudomembranous colitis (PMC) are increasing worldwide, it is important to study the simple predictive risk factors for PMC among patients with hospital-acquired diar-rhea (HAD). This study focused on identifying the clinical risk factors that can easily predict PMC. Methods: The presumed HAD patients were prospectively recruited at the Hallym Uni-versity Kangdong Sacred Heart Hospital. Results: Age of 70 and older (adjusted odds ratio [OR], 1.76; 95% confidence interval [CI], 1.12 to 0.75), use of proton pump inhibitors (ad-justed OR, 4.07; 95% CI, 2.512 to 6.57), use of cephalospo-rins (adjusted OR, 2.99; 95% CI, 1.82 to 4.94), and underly-ing cancer (adjusted OR, 1.72; 95% CI, 1.04 to 2.82) were independent risk factors for PMC in the multivariate logistic regression analysis. The prevalence of PMC was very low in the patients with HAD who exhibited no risk factors. Conclu-sions: The risk factors for PMC in patients with HAD included cephalosporin use, proton pump inhibitor use, old age, and cancer. Considering the strongly negative predictive values of these risk factors, endoscopic evaluation can be delayed in patients with HAD without risk of developing PMC. (Gut Liver 2014;8:41-48)