Abstract: Objective To study the mutagenicity and genotoxicity of methyl tertiary butyl ether(MTBE).Methods Ames test was applied to detectits genotoxicity.The subchronic oral MTBE test,Single Cell Electrophoresis Assay(SCEA) were carried out to find the DNA damage in blood nucleolated cells of male Sprague-Dawley rats.Results MTBE did not showany mutagenic potent ial in Ames assay(TA98,TA10 strains)with or without rat live-rderived metabolic activation system(S-9),and also there was no significant difference in the DNA damage betw een the exposure and control group in sub-chronic test.Conclusion No mutagenicity appeared in this series of genotoxicigy tests.Further study must be performed on the effect of MTBE on the cell cycle to detect whether the MTBE had some degree of potential mutagenicity.