The promise of hydrogen resides in its being a clean and efficient energy source. This paper examines this promise in the context of hydrogen production, transportation, delivery and end use. Several fossil fuel feedstocks as well as renewable sources are examined. The cost and efficiency analysis as well as a potential market scenario for the development of light duty vehicles using hydrogen fuel cells are presented from a recent NRC report (2004). Multiple challenges associated with the implementation of hydrogen for the light duty vehicles are discussed. This presents a number of exciting research opportunities for most chemical engineers including process systems subgroup.