The dynamic response of the Ziff, Gulari, and Barshad model for the catalytic oxidation of CO, to a periodic variation of the external pressure is studied close to the CO-poisoning transition. Due to the applied pressure, a considerable enhancement in the catalytic activity is observed when the system is briefly driven into the CO-poisoned state. However, saturation of catalysts' surface can be induced by applying signals of either long period or high amplitude. (C) 2000 American Institute of Physics. [S0021-9606(00)50405-X].