The catalytic control of automobile exhaust pollutants (hydrocarbons, carbon monoxide, nitrogen oxides) is now a common practice in the United States and Japan, and there are strong indications that the technology may be introduced in other parts of the world in the coming years. The simultaneous conversion of all three of the above pollutants is achieved by the near-stoichiometric operation of noble metal catalysts which are supported either on alumina particles or on alumina-washcoated cordierite monoliths, A summary of the developments which lead to this technology can be found, e. g., in Hegedus and Gumbleton [1] and references therein.