Emtricitabine Given Once A Day With Other Anti-HIV Drugs in Children With HIV

Inclusion Criteria Children may be eligible for this study if they: * Are at least 3 months old and no older than 17 years of age. This is the age the child needs to be at the time they begin the study. * Are HIV positive. * Weigh more than 5.5 pounds. A newborn child must have reached at least 38 weeks of gestation. * Have or have not taken anti-HIV drugs. Those that have not must have a viral load between 5,000 and 500,000 copies/ml at screening. Those that have must have been taking anti-HIV drugs, including lamivudine, for at least 3 months and have a viral load of no more than 400 copies/ml at screening. * Have a CD4 count of more than 200 cells/mm3. * Have written consent from parent or guardian. * Are willing to use effective birth control during the study and for 1 month after the last dose of emtricitabine, if sexually active. Exclusion Criteria Children will not be eligible for this study if they: * Are pregnant or breast-feeding. * Cannot follow the visit or dosing schedule or are not available for 1 year. * Have taken experimental drugs or vaccines (except for emivirine and experimental forms of approved drugs) within 30 days of study start. * Have nerve damage in their arms or legs. * Have trouble eating or taking drugs. * Have serious diarrhea within 30 days before study entry. * Have had any serious illness within 30 days of study screening. Any treatment must have been finished 14 days before study entry. * Have had an AIDS-related (opportunistic) disease within 12 months of screening. * Are being treated for tuberculosis. * Have had pancreatitis. * Require certain drugs.