Patients who have recovered from past HCV exposure (positive anti-HCV but negative HCV viremia and absent liver disease).
Patients with asymptomatic HCV infection (positive anti-HCV and HCV viremia, but persistently normal or minimally elevated ALT and normal or mild disease on liver biopsy).
Patients with active liver disease (positive anti-HCV and HCV viremia, persistently elevated ALT and/or moderate disease on liver biopsy).
Patients with active extrahepatic manifestations of HCV infection (cryoglobulinemia, glomerulonephritis, vasculitis, etc.).
Patients with rapidly progressive, severe liver disease and/or hepatocellular carcinoma.
Patients who have undergone or are undergoing treatment.
Patients from a single-source outbreak of HCV infections (in which the viral factors should be identical and the patients are often from a homogeneous population with less genetic variability).
HCV infected family members and twins.
Patients with other forms of liver disease including HBV infection, primary biliary cirrhosis, autoimmune hepatitis, nonalcoholic steatohepatitis, hemochromatosis, and Wilson's Disease, as well as normal volunteers.
Adult subjects with a Hct of less than 30 or pediatric subjects less than 25 will be excluded.
Children with HCV infection younger than 2 years of age will be excluded.
Unaffected healthy volunteers who are minors are not eligible for this study.