The first step in the assessment of biocompatibility of new biomaterials is in vitro toxicity tests that include cytotoxicity and genotoxicity. In this study, we applied genetically engineered yeast cells to the assessment of cellular oxidative stress, a major cytotoxic effect of metal-based biomaterials, and genotoxicity. For measurement of oxidative stress, a gene of green fluorescence protein (GFP) was fused to a chromosomal copy of SOD1 gene, of which encoded protein is expressed responding to intracellular oxidative stress caused by most metal ions. After exposure to metal ions, the yeast cells exhibited fluorescence dose-dependently even at sublethal concentrations. For genotoxicity test, a multicopy plasmid bearing a RAD54 promoter fused to GFP was used as a sensing part of yeast cells. The monomers of dental resin (HEMA, TEGDMA and UDMA) were tested for their mutagenicity. Among the monomers, TEGDMA exhibited the increase of fluorescence. This result indicates that the test with yeast may produce the scores of genotoxicity closer to those obtained with mammalian cells rather than bacteria. In conclusion, this study showed the usefulness of yeast cells for in vitro biocompatibility test of biomaterials. (c) 2005 Elsevier B.V. All rights reserved.