To estimate the prevalence and predictors of hepatitis C virus (HCV) infection among inmates, a cross-sectional survey was conducted in 1994 among inmates entering six reception centers of the California Department of Corrections. Discarded serum samples were tested for antibodies to human immunodeficiency virus (HIV), HCV, hepatitis B core, and hepatitis B surface antigen (HBsAg). Of 4,513 inmates in this study, 87.0% were men and 13.0% were women. Among male inmates, 39.4% were anti-HCV-positive; by race/ethnicity, prevalences were highest among whites (49.1%). Among female inmates, 53.5% were anti-HCV-positive; the prevalence was highest among Latinas (69.7%). In addition, rates for HIV were 2.5% for men and 3.1% for women; and for HBsAg, 2.2% (men) and 1.2% (women). These data indicate that HCV infection is common among both men and women entering prison. The high seroprevalence of anti-HCV-positive inmates may reflect an increased prevalence of high-risk behaviors and should be of concern to the communities to which these inmates will be released.