This study highlights the increasing prevalence and severity of C difficile colitis in hospitalized patients in the United States from 1993 to 2003. As indicated by the authors, these epidemiologic findings have been corroborated by several other studies. The use of the NIS in this study allowed for many cases of C difficile in the United States to be identified. However, this study is limited by the lack of a denominator indicating the number of C difficile toxin studies performed, the lack of confirmation of the disease in all cases, and a bias toward Medicare (older) patients.