Examine the antiretroviral activity of ZDV/3TC/NVP in vertically-infected infants and children aged 15 days to 2 years, and ZDV/3TC/NVP/1592 in vertically-infected infants and children aged 30 days to 2 years. Assess the HIV-1 and CD4/CD8 t-cell kinetics, activation and maturtion. Test the concept that early use of potent, combination antiretroviral therapy will allow the long term control of viral replication with preservation of normal immune function.