Abstract: A catalyst suitable, for example, for treatment of cat exhaust emissions is prepared by providing a substrate with a continuous adherent, surface layer of a carrier material for catalytic material by providing on the substrate a layer of carrier material, at least part of which comprises a gel, and firing; and sputtering catalytic material onto the surface layer by bombarding a source of the catalytic material in the neighbourhood of the surface layer with energetic ions, the conditions of atmosphere and selectivity of ions permitted to bombard the catalytic material being such that co-deposition upon the surface layer of unwanted material is avoided.