The regulated pollutants (CO, HC and NOx) and unregulated pollutants (volatile organic compounds and carbonyl compounds) , emitted from a dual fuel vehicle fueled with gasoline and E10 fuel, are measured under a transient cycle and steady modes. The impacts of a three-way catalyst (TWC) are investigated for the two types of fuels. The measured results show that NOx and acetaldehyde emitted from the E10-fueled car are much more than that from the gasoline-fueled car under the same modes. On the basis of maximum incremental reactivity (MIR) factors and emissions of organic gases, the ozone specific reactivity of the tailpipe gases are evaluated.