This study will evaluate hepatitis C virus (HCV) infection in blood donors who test positive for antibodies to this virus. Most HCV-infected people do not become ill and are not aware that they have hepatitis or have had it in the past. Some infected people recover completely, whereas others remain chronically infected. The study will try to define infectivity of anti-HCV positive individuals, routes of transmission of the virus, and the number of HCV-infected persons who have evidence of liver disease.