OBJECTIVE Hepatitis C virus (HCV) infection is the leading cause of liver failure in adulthood. Although the prevalence of HCV is reportedly as high as 80% in incarcerated adult populations, little is known about the prevalence of HCV in incarcerated juvenile populations. The purpose of this study was to determine the prevalence of HCV and high-risk behaviors in a population of incarcerated youths. METHODS We conducted a cross-sectional prevalence study of HCV infection in youths who were admitted to a juvenile detention center between September 1999 and January 2001. Subjects were asked questions regarding behaviors that might put them at risk for acquiring HCV, and blood was drawn for HCV antibody testing. Qualitative HCV RNA testing was performed on antibody-positive subjects. RESULTS Seventy-four percent (n = 305) of youths consented to participate in the seroprevalence study. HCV risk behaviors were common in this population: sexual activity (70%), intravenous drug use (6%), intranasal drug use (32%), body piercing (53%), and tattoos (33%). Six study youths (2%) were HCV antibody positive; 4 of these subjects were also HCV RNA positive. HCV-positive status was significantly associated with history of intravenous drug use and having had a sexually transmitted disease. Only 17% of study participants could correctly identify behaviors that might put them at risk for HCV. CONCLUSIONS The prevalence of HCV in incarcerated youths is higher than in the general pediatric population but not yet at adult levels of prevalence. Given the high prevalence of risk factors in this population, future studies should address the need for targeted HCV screening and education of incarcerated youths regarding risks for HCV.