A new type of metal supported catalyst for gasoline engines has been developed. The catalyst's excellent conversion efficiency is based on the use of high cell densities. With the new Z-flow construction the substrate has been turned semi transversely to the flow direction. The substrate length has been shortened and the cross section area increased, thus ensuring pressure drop characteristics are kept competetive with conventional converter systems. In this work the theoretical background for the causes of pressure drop in the catalyst and advantages of high cell densities are presented. The catalyst function has been studied with differing cell densities up to 1600 cpsi. The performance of the new Z-flow catalyst has been compared with several commercially available ceramic catalysts. The results show that when employing high cell density catalysts in conjunction with the Z-flow converter construction, considerably smaller catalyst volumes and less precious metal amounts are required.