The energy crisis of recent years is primarily a petroleum shortage. Thus because the depletion of world petroleum reserves can now be foreseen, a new form of portable energy will be needed to power gasoline and diesel engines. Alcohol is a portable, clean-burning form of energy that is already in limited use as a partial replacement for gasoline and diesel. The state of the art of gasohol （a blend containing, by volume, 10∼20 % anhydrous alcohol and 80∼90 % gasoline） and diesohol (a blend containing, by volume, 10 % or more anhydrous alcohol and 90 % or less diesel fuel) as conventional engine fuels is reviewed in two parts, the former in Part (I) and the latter in Part(II). Physico-chemical properties and performance characteristics of the blended fuels are discussed in conjunction with conventional engines. Alcohol gasoline blends exhibit, from one stand point, near interchangeability with, and from a different stand point, better performance characteristics than gasoline. Also, economics aspects including that of producing ethyl alcohol from biomass are discussed.