Patients with primary sclerosing cholangitis (PSC) have a significantly increased risk of developing cholangiocarcinoma (CCA). Risk factors for developing such a complication are not well defined. We conducted a multicenter, case-control study to determine the risk factors and possible predictors for CCA in patients with PSC. The demographic, clinical, and laboratory features of 26 PSC patients with CCA diagnosed over a 7-year period at eight academic centers were compared with 87 patients with PSC but no CCA (controls). There was no statistically significant difference in demographics, smoking, signs or symptoms or complications of PSC, indices of disease severity (Mayo Risk score or Child-Pugh score), frequency or duration or complications of inflammatory bowel disease (IBD), frequency of biliary surgery, or therapeutic endoscopy between the two groups. Alcohol consumption was significantly associated with CCA in patients with PSC (odds ratio: 2.95; 95% CI: 1.04-8.3). Serum carbohydrate antigen 19-9 (CA 19-9) was significantly higher in patients with CCA than those without (177 +/- 89 and 61 +/- 58 U/mL, respectively; P =.002). A serum CA 19-9 level > 100 U/mL had 75% sensitivity and 80% specificity in identifying PSC patients with CCA. In conclusion, alcohol consumption was a risk factor for having CCA in PSC patients. The indices of severity of liver disease were not associated with CCA in patients with PSC. Serum CA 19-9 appeared to have good ability to discriminate PSC patients with and without CCA.