The effect of gamma-irradiation on mitotic segregation and intergenic reciprocal mitotic recombination between the centromere and the ade2 locus of rad sensitive Saccharomyces mutant has been studied in comparison with the wild type RAD. These strains homozygous for either RAD or rad54 gene, showed gamma-rays induced mitotic segregation and reciprocal mitotic recombination. Within a dose range resulting in an equal survival, fraction induced mitotic segregation and intergenic reciprocal recombination was greater for the RAD strain. Rad54 mutation increased the spontaneous mitotic segregation and mitotic reciprocal recombination in comparison with the rad strain.