This is a pilot study to evaluate the ability of highly active antiretroviral therapy administered to children with HIV-1 infection to effect immunoreconstitution in children with HIV-1 infection. In addition, this study will determine the safety of combination therapy with ritonavir, nevirapine and stavudine (d4T) as well as the anti-HIV activity of combination therapy with ritonavir, nevirapine and stavudine. A total of 25 HIV-1 infected children will be studied, including both moderately and severely immunocompromised individuals. The children will be treated with ritonavir, nevirapine and stavudine or with predefined drug substitutions in the case of intolerance. Immunoreconstitution, defined as the repopulation of naive T cells, will be studied by determining the presence and extent of production of new naive (thymic derived) CD4+ T cells and their T cell receptor repertoire. Drug pharmacokinetic profiles in this regimen will be examined.