OBJECTIVE In order to compare the mutagenicity of the gasoline-fueled vehicle exhaust (gasoline exhaust for short) and the methanol-fueled vehicle exhaust (methanol exhaust for short), provide a scientific basis for replacement gasoline by methanol as fuel in vehicle. METHODS The Ames assay and A549 cell micronucleus test in vitro were applied to compare the mutagenicity of gasoline-fueled vehicle exhaust and methanol-fueled vehicle exhaust. RESULTS The results showed that the gasoline-fueled vehicle exhaust expressed evident mutagenicity in Ames assay (TA98 strain) with or without rat liver-derived metabolic activation system (S9). The mutagenicity increased obviously when S9 was used and showed a good dose-response relationship. However, the methanol-fueled vehicle exhaust did not show any mutagenic potential in Ames assay (TA98, TA100 strains) with or without rat liver-derived metabolic activation system (S9). In A549 cells micronucleus test in vitro, between 0.025 - 0.2JL/ml, the rate of A549 cells micronucleus could be induced by the gasoline-fueled vehicle exhaust. For the methanol-fueled vehicle exhaust, there was no significant differences in the rate of A549 cells micronucleus between the tested groups and control. CONCLUSIONS The results strongly suggested that the gasoline-fueled vehicle exhaust had potential mutagenicity and the methanol-fueled vehicle exhaust did not show any potential mutagenicity. The results also provided a scientific basis for replacement gasoline by methanol as fuel in vehicle.