Repeated dose liver micronucleus assay using clofibrate in young adult rats.

•Repeated-dose micronucleus assays were performed with clofibrate in young–adult rats.•The frequencies of micronucleated cells were examined in the liver and bone marrow.•Positive results were observed in the liver in 14- and 28-day studies.•Negative results were observed in the bone marrow in 14-day study.•Liver micronucleus assays may be useful for detection of liver carcinogens.