Abstract: The present invention relates to a novel catalyst comprising at least one support material, rhodium as active metal either alone or in combination with further active metals from the platinum metal group and also at least one rare earth oxide as promoter, where the mass ratio of rhodium to the sum of further active metals from the platinum metal group is at least 1:4.5. In contrast to the catalysts of the prior art, aging or deactivation caused by sulphur-containing deposits can be minimised in the catalyst of the invention. The present invention further provides a method of purifying exhaust gas from internal combustion engines which are predominantly operated in a lean mode and in which the catalysts of the invention are used in a rich-lean cycle.