This study will determine the amount of liver scarring (fibrosis) or liver damage in people infected with 1) hepatitis B virus (HBV, a virus that can infect the liver); 2) HIV (the virus that causes AIDS); 3) both HBV and HIV; and 4) neither HBV nor HIV. Liver fibrosis and liver damage can have many causes, including alcohol, certain medicines, exposure to some contaminated foods and infections with viruses that affect the liver (such as HBV). About 25 million people in sub-Saharan Africa are infected with HIV and about 50 million with chronic HBV, yet very little information is available on how many people are infected with both viruses and the medical implications of co-infection.