A large variety of compounds have been reported to inhibit the replication of human immunodeficiency virus (HIV). The compounds that have been most intensively pursued for the treatment of HIV infection belong to three classes: nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs). Within each of these classes, a number of compounds have been identified that inhibit HIV replication at nanomolar concentrations which are 10(4)- to 10(5)-fold lower than the cytotoxic concentrations. Yet, the potential usefulness of these compounds seems to be compromised by the rapid emergence of virus drug resistance. Here, we describe a strategy that, at least in cell culture, prevents the development of resistance. This strategy is based on the use, from the beginning, of sufficiently high drug concentrations. When added at such concentrations, that for some of the NNRTIs did not have to be higher than 10-100 times their 50% effective concentration (EC50), these compounds completely suppressed ("knocked out") HIV-1 replication in cell culture, and thus prevented drug-resistant virus strains from emerging. This "knock out" effect could be achieved for longer times and at lower drug concentrations when the compounds were combined (i.e. NNRTIs with one another or with NRTIs) than when used individually. Thus, when used at the appropriate doses, as such or in combination, NNRTIs proved able to completely clear ("cure") HIV-1-infected cell cultures from the virus.