In July 1989, the Bush administration proposed a new, dramatic approach to constructing clean air legislation. In particular, the Bush proposal calls for using alternative fuels as an important component to reducing urban ozone and carbon monoxide. This paper summarizes the Bush proposal, looks briefly at other options to reduce urban air pollution, and empirically evaluates the cost effectiveness of alternative fuels as an air pollution control strategy. The paper finds that the cost per ton of emissions reduced-the measure of cost effectiveness-varies dramatically as the price of gasoline vis a vis the price of the alternative fuel changes. For this reason, the authors believe that new clean air legislation should allow for great flexibility so as to allow states to incorporate alternative fuels when they are cost effective. If oil prices turn out to be lower than expected, then forcing urban centers to adopt relatively more expensive alternative fuels would impose high costs. Copyright 1990 Western Economic Association International.