A re patients with inflammatory bowel disease (IBD) at increased risk for herpes zoster? Gupta et al used the General Practice Research Database from 1988 -1997, a database of primary care medical records from the United Kingdom representing 6% of the population, to perform a retrospective cohort study and a retrospective nested casecontrol study to answer this question. Previous work has proven the accuracy of this database for epidemiologic studies, including those involving IBD. In the cohort study, which compared IBD with non-IBD patients, 7823 Crohn's disease (CD) and 11,930 ulcerative colitis (UC) patients were matched on age, sex, and primary care practice to 79,563 randomly selected controls without IBD. In the nested casecontrol study, 185 CD patients and 266 UC patients with zoster were matched on sex and year of birth to 1787 IBD patients without zoster. The results of the cohort study showed that the incidence of zoster was higher in patients with IBD compared with their matched non-IBD controls (UC incidence rate ratio, 1.21; 95% confidence interval [CI], 1.05-1.40; CD incidence rate ratio, 1.61; 95% CI, 1.35-1.92). In the nested case-control study of IBD patients, receipt of a prescription for corticosteroids (adjusted odds ratio [OR], 1.5; 95% CI, 1.1-2.2) or azathioprine/6-mercaptopurine (adjusted OR, 3.1; 95% CI, 1.7-5.6) were both associated with zoster. No association between the use of mesalamine and zoster was noted. The risk of zoster was greater in CD than UC patients. The authors suggest that the dysregulation of the immune system during active IBD creates a risk for zoster, and that immuosuppressive medications provide a risk that is as or even more important. This is the first large retrospective database-driven study looking at the risk and details of herpes zoster in IBD patients, and supplies important information about the risk of zoster in IBD patients. Strengths of the study include a well-defined source population in the database with an internal control group, a large sample size, a previously validated reliability of the IBD diagnosis, and the ability to examine subgroups of patients treated with specific medications. As with any retrospective study, there are inherent weaknesses.