This study evaluates the influence of speciated emissions on ozone reactivity using the values of Maximum Incremental Reactivity published by the California Air Resources Board in September 1990.To evaluate the influence of fuels and vehicle specifications on speciated emissions and ozone reactivity, three different fuels (gasoline, reformulated gasoline, and methanol (M85)) were used. Hydrocarbon species were measured using three types of gas chromatographs. Aldehydes were collected in a dry cartridge and measured by High Performance Liquid Chromatograhpy (HPLC). Alcohols were collected using impingers and measured by a gas chromatograph.In the case of gasoline, as Non-methane Organic Gas (NMOG) is reduced, the proportion of speciated emissions with high ozone reactivity decreases, and this tends to lower Ozone Forming Potential (OFP). In the case of reformulated gasoline, OFP does not decrease, but Non-methane Hydrocarbons (NMHC) do as NMOG is reduced. In the case of M85, it is difficult to find a general correlation between NMOG and OFP.