OBJECTIVES We described hepatitis C virus antibody (anti-HCV) prevalence in a state prison system and retrospectively evaluated the case-finding performance of targeted testing of the 1945 to 1965 birth cohort in this population. METHODS We used observational data from universal testing of Pennsylvania state prison entrants (June 2004-December 2012) to determine anti-HCV prevalence by birth cohort. We compared anti-HCV prevalence and the burden of anti-HCV in the 1945 to 1965 birth cohort with that in all other birth years. RESULTS Anti-HCV prevalence among 101,727 adults entering prison was 18.1%. Prevalence was highest among those born from 1945 to 1965, but most anti-HCV cases were in people born after 1965. Targeted testing of the 1945 to 1965 birth cohort would have identified a decreasing proportion of cases with time. CONCLUSIONS HCV is endemic in correctional populations. Targeted testing of the 1945 to 1965 birth cohort would produce a high yield of positive test results but would identify only a minority of cases. We recommend universal anti-HCV screening in correctional settings to allow for maximum case identification, secondary prevention, and treatment of affected prisoners.