Secondary: To evaluate the effect of nevirapine on surrogate markers. The anti-HIV agent nevirapine is associated with rapid emergence of resistance when administered alone or in combination with zidovudine to HIV-infected patients with CD4 counts <= 400 cells/mm3. In persons with less advanced HIV disease and less viral burden, the emergence of resistance may be delayed, thus permitting evaluation for beneficial effect in a population where there is currently no established therapy.