A series of monomeric acrylate/methacrylate esters (methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate) as well as acrylic acid were examined for genotoxic activity in L5178Y mouse lymphoma cells without exogenous activation. All five compounds induced concentration dependent increases in mutant frequency. Small-colony, TFT-resistant mutants were primarily induced which suggest that these compounds may act via a clastogenic mechanism. The prediction was confirmed by the finding that all five compounds produced gross aberrations in mouse lymphoma cells. The two acrylates were much more potent in their response than acrylic acid. The two methacrylates required larger quantities of compound to induce a positive response. The evidence suggests that the genotoxicity of these compounds is most likely due to a clastogenic mechanism.