To assess the safety and tolerance of multiple oral doses of Nevirapine (BI-RG-587). To generate data on the pharmacokinetics and dose proportionality of Nevirapine with multiple dosing. To characterize the pattern of virological activity in vivo. Improvement in virological end points will be examined for association with dose and absorption. To determine whether development of resistance is reflected in return of virological activity and, if so, when markers reflect this resistance. To determine if improvements of immunological endpoints are detectable in the number of patients studied. A compound free of the toxic effects of nucleoside chain terminators such as zidovudine (AZT) may have an advantage over currently available treatments for HIV infection. Such a compound has further advantages if it is active against AZT-resistant isolates. Nevirapine (BI-RG-587) has shown in vitro inhibitory activity against HIV-1 reverse transcriptase (RT). The molecular mechanism of the RT inhibitory effect is hypothesized to be non-competitive inhibition due to its binding to an RT site distinct from those for the RNA template primer, the deoxynucleotide triphosphate or the RNase H catalytic site.