Seven common fuels are compared for their utility as hydrogen sources for proton-exchange-membrane fuel cells used in automotive propulsion. Methanol, natural gas, gasoline. diesel fuel, aviation jet fuel, ethanol, and hydrogen are the fuels considered. Except for steam-reforming methanol and using pure hydrogen, all processes for generating hydrogen from these fuels require water-gas shift reactors of significant size. This occurs because their higher processing temperatures produce unacceptably large amounts of CO. All processes require low- or zero-sulfur fuels. and this may add cost to some of them. Fuels produced by pure steam-reforming contain similar to 70-80% hydrogen, those by pure partial oxidation similar to 35-45%. The lower percentages may adversely affect cell performance. Pure steam-reforming suffers from poor transient operation. Theoretical input energies do not differ markedly among the processes for generating hydrogen from organic-chemical fuels. Pure hydrogen has formidable distribution and storage difficulties. The factors considered in this work make some combination of partial oxidation and steam-reforming of methanol technically the leading candidate for on-board generation of hydrogen for automotive propulsion. The possible use of methanol suffers from a lack of infrastructure and solubility in water combined with toxicity. Methanol's disadvantages have stimulated extensive current research employing other primary fuels for this purpose.