Due to the course of registration of pesticides in Japan, the Food Safety Commission (FSC) has the responsibility to make a risk assessment of residual pesticides and related chemicals through foods. Among the set of safety evaluations for pesticides, genotoxicity assay data are mandatory. The standard test battery for this evaluation consists of a bacterial gene mutation assay, in vitro mammalian chromosomal aberrations and/or other chromosome damage assay, and in vivo rodent micronucleus assay. These assay outcomes are used for mechanistic consideration of carcinogenicity, if any. As a rule, if a certain substance is carcinogenic and the mechanism of it includes genotoxicity, the FSC might decide it is not possible to establish the acceptable daily intake of that pesticide. Therefore, the information about genotoxicity is critical for potentially carcinogenic chemicals, whether the applied substance will be adopted and permitted for use or not as pesticides. It is important to assess fairly, carefully, and transparently, but feasible, rapid, and efficient assessment also should be taken into account. Therefore, needless to say, the assay(s) should have the sensitivity to detect potent mutagens. It is also important to be aware that the required data set should be consisted of reliable assays without certain assay(s) that give(s) false positive information or offer less of a contribution for the safety assessment.