Several novel, structurally distinct classes of specific human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) nonnucleoside inhibitors have been described recently. These include the pyridinone derivatives L-697,639, L-697,661, and L-696,229 as well as BI-RG-587 and the tetrahydroimidazo[4,5,1-j,k]-benzodiazepin-2(1H)-one and -thione compounds. Previous studies have implicated involvement of the RT amino acid residues at positions 103, 181, and 188 in the activity of the compounds. Accordingly, HIV-1 RT mutants containing a series of amino acid substitutions at these positions were constructed. The relative resistance of purified mutant enzymes to each of the inhibitors was assessed. This analysis established the functional equivalence of the three inhibitor classes and provided evidence for the interaction of the 103 site with the 181/188 region. Amino acid substitutions at these positions were also found to influence RT sensitivity to inhibition by phosphonoformate, thereby suggesting a close association between this pyrophosphate analog's binding site in RT and the binding site of the nonnucleoside inhibitors. In addition, aromatic stacking of the amino acid side groups at residues 181 and 188 was suggested to be required for inhibitor activity.