Industrial application of fuel cell technology requires suitable electrocatalysts.This is true for all different types of fuel cells. These catalysts are responsible for the oxidation of the fuel (i.e. hydrogen, hydrogen rich gases or methanol) as well as for the oxygen reduction. This paper focuses on solid polymer electrolyte fuel cell systems for mobile applications. Here the demands on the catalyst are most severe due to the low-temperature operating regime. Two system configurations are possible: either the carbon containing fuel is processed by a fuel converter to a hydrogen rich gas mixture and this in turn is fed into the fuel cell. Alternatively fuels such as methanol can be supplied directly into the fuel cell. In the first case, contaminations of CO, in the feed gas have to be taken into account. These strongly absorbs on the surface of the catalysts (carbon- supported Pt or Pt-alloys) thereby inhibiting the hydrogen oxidation reaction. Electro-oxidation mechanisms of adsorbed CO as well as methanol-as an example for a direct fuel cell system-is discussed on Pt-Ru and other catalysts. Finally catalysts for methanol and hydrocarbon reforming reactions as well as for the shift reaction are reviewed.