The reverse transcriptase activity measured in yeast cells was shown to be sensitive to inhibitors of HIV-1 RT like 8Cl-TIBO, a well-characterized nonnucleoside RT inhibitor of HIV-1 RT while the hybrid constructions that express NNRTI-resistant RT variants of HIV-1 are insensitive to8Cl-TIBO demonstrating in yeast the specificity of inhibition in this assay.