A large number of vehicles are now running on gaseous fuels. Most are using liquefied petroleum gas (LPG), and some are using natural gas (NG). Published studies have listed the advantages and disadvantages of such conversions, but these have had an unexpected degree of understatement and take a very stringent view of the emission advantage, giving the impression that vehicles using gaseous fuels cannot compete with emission control of the clean gasoline-powered vehicles planned for 1975. This conclusion will probably be proved erroneous when all data are available. As compared to clean 1975 gasoline vehicles, gaseous-fueled vehicles will probably be cheaper to run and more reliable. Disadvantages include limited distribution of gaseous fuels, limited fuel-carrying capacity, some regulatory limitations, and a need for more highly developed hardware. Despite these problems, there is a small but important market where conversion will be very profitable for the owner and the community.