DNA damage and other forms of stress are believed to be important factors in reducing the efficiency of in vitro embryo transfer techniques in farm animals. The expression of mRNAs from stress-responsive genes such as gadd153 (CHOP-10, ddit3) may provide a means of assessing the quality of embryos produced in vitro. Treatment of bovine granulosa cell cultures with the DNA-damaging agents, methyl methane-sulphonate (MMS) or sodium arsenite, induced the expression of an mRNA, which hybridized with the hamster gadd153 cDNA. Part of the corresponding bovine cDNA was amplified by nested polymerase chain reaction (PCR), cloned, and sequenced. Using a sensitive reverse transcriptase-PCR assay we have investigated the expression of gadd153 and β-actin in blastocyst-stage bovine embryos treated with MMS or sodium arsenite. Both agents produced an increase in the ratio of gadd153 mRNA relative to β-actin. These results show that there are changes in gene expression in blastocyst-stage bovine embryos in response to genotoxic stress, suggesting that an increase in gadd153 mRNA is a useful marker of DNA damage and metabolic stress in preimplantation embryos.