In the United States, the annual number of newly acquired acute hepatitis C virus (HCV) infections has declined from an estimated 180,000 in the mid 1980s to an estimated 28,000 in 1995. Approximately 25% to 30% of these infections are clinically apparent cases that are sufficiently symptomatic to gain medical attention. Deaths from fulminant hepatitis C are rare. The prevalence of antibody to HCV (anti-HCV) in the general population of the United States is 1.8%, corresponding to an estimated 3.9 million Americans infected with HCV, and an estimated 8,000 to 10,000 deaths each year result from HCV-associated chronic liver disease. HCV infection affects persons of all ages, but most acute cases of hepatitis C and the highest prevalence of anti-HCV are found among young adults. The highest proportion both of incident cases and prevalent infections is among whites, but the highest incidence and prevalence rates are among non-white racial/ethnic groups. In the past, transfusion of blood and blood products was an important source of HCV transmission, but currently, high-risk drug and sexual exposures account for most HCV transmission. Although the incidence of acute hepatitis C has declined, there is a large reservoir of chronically infected Americans who can serve as a source of transmission to others and who are at risk of the severe consequences of chronic liver disease.