While there are around 25 million HIV-infected persons in sub-Saharan Africa, there are also an estimated 50 million with chronic hepatitis B virus (HBV) infection. Yet data from Africa on the prevalence and clinical implications of HIV/HBV co-infection are sparse or unavailable. The scale-up of' HIV treatment with antiretroviral medication (ARVs) in Africa, should result in substantial reductions in morbidity and mortality. In developed countries, however, improved survival with highly active antiretroviral therapy (HAART) has been associated with notable increases in mortality due to liver disease among HIV-infected persons. Also, persons co-infected with hepatitis viruses have significantly higher liver-related toxicity with ARVs compared to persons infected with HIV alone. Our protocol will investigate predictors of liver disease among co-infected participants. The proposed study directly addresses the problem of HIV/HBV co-infection by examining the association of HBV viral markers with the development of significant liver fibrosis (defined by transient elastography). In addition to strengthening the clinical research capacity of our Ugandan colleagues, completion of our study aims will provide needed information for understanding the complex interaction of HBV and HIV, for projecting the future burden of liver disease related to the HIV epidemic, for clinical management of HBV infection in the setting of co-infection with HIV, and for optimizing the benefits while mitigating the potential deleterious consequences of antiretroviral programs in Africa.