Background: Clostridium difficile infection (CDI) is becoming prevalent in general population as well as in patients with inflammatory bowel disease (IBD). Aim: The aim of the study was to identify risk factors for CDI in patients with ulcerative colitis (UC) and to assess outcome of UC in patients following CDI. Methods: UC inpatients or outpatients who had positive results for C. difficile toxins A and B between 2000 and 2006 were identified (N = 39) and matched for age and gender to UC patients who were negative C. difficile toxins and had never been diagnosed with CDI (N = 39). Records were reviewed for adverse clinical outcome, defined as colectomy within 3 months of C. difficile testing. Conditional logistic regression was used to analyze multivariable association to identify risk factors for CDI and for adverse clinical outcome. Results: A total of 78 subjects were analyzed, 60% were males. Median age was 39. Among 39 patients with CDI, 20 (47.2%) were diagnosed as outpatients, 50% failed treatment with the first antibiotic monotherapy, and 21.2% had recurrent infection. Antibiotic exposure within 30 days prior to C. difficile testing was found to be associated with an increased risk for CDI with an odds ratio of 12.0(95% CI 1.2, 124.2) Subsequent colectomy within 3 months after CDI diagnosis, was not associated with CDI in both univariable and multivariable analyses. After adjusting for CDI, lack of 5-aminosalicylic acid (ASA) in the treatment regimen was significantly associated with colectomy with an odds ratio of 3.3 (95% Cl: 1.2, 9.4). There was no UC- or CDI-associated mortality in this case series. Conclusions: Recent antibiotic exposure was a risk factor for CD! in UC patients. Interestingly, CD! does not seem to adversely affect short-term adverse clinical outcome (colectomy). (C) 2010 European Crohn's and Colitis Organisation. Published by Elsevier B.V. All rights reserved.