"INTRODUCTION Gaseous@ fuels (propane (LPG) @ compressed natural gas (CNG) @ and liquefied natural gas (LNG)@ as substitutes for gasoline in today's cars@ have been shown to reduce exhaust emissions of ""harmful pollutants."" This can be attributed primarily to the inherently better mixing characteristics of gaseous fuels@ as compared to liquid fuels@ in a premixed charge engine. Consequently@ many investigators have reported the merits of the gaseous fuels@ demonstrating these particular fuels to have significantly reduced automotive emissions as compared to gasoline@ Considerations of fuel availability on an overall national as well as regional supply situation have also been touched on in several symposia and government sponsored studies. Economic evaluations of the merits of such conversions generally have been optimistic@ being based on preferential assumptions of conversion and fuel costs and tax abatements. This report presents an assessment of published information on the potential impact of adoption of gaseous fuels to reduce automotive emissions from existing and future motor vehicles as a means of achieving improved air quality in the 1975-80 period. In doing so@ only the major considerations of vehicle emissions@ fuel and equipment costs and availability and overall impact on emissions from all sources have been addressed. Also@ consideration of hydrogen as a motor fuel was not deemed to be within the scope of this report as the present technological conditions make it highly improbable that hydrogen can be a serious contender within the time span studied."