The purpose of this study is to examine the effect of GB virus C (GBV-C) on the natural history of chronic hepatitis C virus (HCV) infection in subjects co-infected with HIV and HCV. The other aspect of the study is to assess the effect of GBV-C on the severity of liver disease due to chronic hepatitis C in subjects co-infected with HIV and HCV. This will be done by determining the point prevalence of co-infection retrospectively then following that cohort prospectively. In addition, further individuals will be recruited in a prospective manner.