The interaction of six mutator genes of the yeast Saccharomyces cerevisiae with respect to UV-induced mutagenesis was studied. To this effect, double mutants with a genotype containing pairs of mutations at genes analyzed were synthesized. Analysis of the type of interaction of these mutations revealed four epistatic gene groups: (1) HIM1, HSM3, and HSM6; (2) HSM1; (3) HSM2; and (4) HIM2 and HIM3. The possible role of genes studied in different repair pathways of mispaired bases was discussed.