A mounting support for a catalyst body which is adapted to be installed into an exhaust gas line of an internal combustion engine; the forces necessary for fixing the catalyst body which act in the longitudinal direction are thereby produced by walls of the mounting support which are located in front of and/or to the rear of the catalyst body, as viewed in the longitudinal direction of the mounting support, on that side on which the forces act laterally on the catalyst body; these walls support themselves at a distance from the catalyst body as measured in the longitudinal direction.