There is debate over the mortality and malignancy risk in people with primary biliary cirrhosis (PBC) and whether this risk is reduced by use of ursodeoxycholic acid. To investigate this issue, we identified 930 people with PBC and 9,202 control subjects from the General Practice Research Database in the United Kingdom. We categorized regular ursodeoxycholic acid as treatment with 6 or more prescriptions and nonregular treatment as less than 6. We found a 2.7-fold increase in mortality for the PBC cohort compared with the general population [adjusted hazard ratio (HR), 2.69; 95% CI, 2.35–3.09]. In those having regular ursodeoxycholic acid (43%), the mortality increase was 2.2-fold (HR, 2.19; 95% CI, 1.66–2.87) and in those not treated 2.7-fold (HR, 2.69; 95% CI, 2.18–3.33). This apparent reduction in mortality was not explained by less severe disease in the ursodeoxycholic acid–treated group. The increased risk of primary liver cancer in ursodeoxycholic acid–treated patients was 3-fold (HR, 3.17; 95% CI, 0.64–15.62), in contrast to an 8-fold increase in those not treated (HR, 7.77; 95% CI, 1.30–46.65). Conclusion: We found that people with PBC had a 3-fold mortality increase when compared with the general population, which was somewhat reduced by regular treatment with ursodeoxycholic acid. However, the observed effect of ursodeoxycholic acid was not statistically significant. (HEPATOLOGY 2007.)