Development work conducted by Volkswagen has shown that for future European applications metal supported catalysts can be considered a viable alternative to ceramics.Novel metal catalysts are discussed under three classifications, viz. MICRO, MIDI and MACRO. The first of these is already in production for retrofitting as well as for new vehicles of less than 1.4 l engine displacement to meet German legislation. The MIDI catalyst has shown similar functional activity to a ceramic catalyst of double the volume. The MACRO catalysts have achieved equivalent activity with 25 per cent less volume.If the metal support is to compete effectively with the ceramic, its present high cost should be reduced.