A method and a system for regenerating, in particular desulfating, storage catalysts in the cleaning of exhaust gas from internal combustion engines. During the regeneration phase the combustion is controlled, initially inside the engine, by a control unit in such a way that the air ratio .lamda. in the exhaust gas is lowered to a first value .lamda..sub.1, and subsequently a feed device for the reducing agent is controlled by the control unit in such a way that the air ratio .lamda. is set at a second, lower value .lamda..sub.2<1. This ensures that the temperatures occurring at the entry side of the storage catalyst are sufficient for effective desulfation without damaging the storage catalyst.