Recently a "Biofuels Promotion and Development Law" was approved in Mexico that requires increasing volumes of renewable to blend into the transportation fuel pool, much of which is likely to be ethanol. Emissions data under the three different driving conditions of the United States FTP-75 certification cycle were obtained for regulated, toxic and carbonyl compounds using recent model year vehicles representing 61% of the typical fleet available in Mexico. Ozone-forming potential and specific reactivity of tailpipe and evaporative emissions were also calculated. Comparison were performed using the traditional methyl-tertiary butyl ether employed in Mexico with an ethanol fuel at the same level of oxygen content, taking into account the current fuel specifications and the stream stocks available at the Mexican refineries. The results suggest that the contribution of cold start to regulated emissions range from 37% to 40% whiles those of toxic from 40% to 47% in both fuels. Results also indicate an increase in the rates of evaporative emissions of higher Specific Reactivy with the ethanol fuel. Estimation of the percent reduction of pollutants using the Complex Model of the USA Environmental Protection Agency suggests that volatile organic compounds will exceeds the limits imposed by the model if vapour pressure of the ethanol gasoline is not properly adjusted. (C) 2010 Elsevier Ltd. All rights reserved.