A fuel cell is an electrochemical engine which converts fuel and oxidant electrochemically into water, other chemical products and electricity. At present, depending on the electrolytic conducting media, five fuel cell types are recognized, the alkaline fuel cell (AFC), the proton exchange membrane fuel cell (PEMFC), the phosphoric acid fuel cell (PAFC), the molten carbonate fuel cell (MCFC), and the solid oxide fuel cell (SOFC). Various types of hydrogen containing fuels can be used in any of the fuel cells, however only the hydrogen-air fueled fuel cell operating at low to medium temperatures (0-450 C) can be considered to meet the zero emission vehicle (ZEV) requirements. Byproducts of the electrochemical reaction of the fuel cells when hydrocarbons and air are used include carbon monoxide, carbon dioxide and at higher temperatures nitrogen oxide. The thermodynamic and practical efficiency of the fuel cells are compared with that of the internal combustion (IC) engine and the diesel engine. The potential of replacing the IC engine and fuel tank with a fuel cell engine and associated fuel supply and the problems and possible solutions connected with this task will be discussed.