The dynamics of deactivation due to parallel fouling is investigated in the case of a rough reactive interface under diffusion-limited conditions. For a first-order reaction, a mathematical method is introduced that permits to analyze the response of the system for any type of interface geometry or input condition. Exact analytical results, such as the lifetime of the catalyst or its total production are calculated. The deactivation dynamics in specific geometries, such as a flat catalytic surface, an infinite pore or a rough surface, are examined. Through these three examples, a general picture of the role of the morphology on the system response is provided. Even more, this approach shows that the determination of a single time response function of a catalyst of unknown morphology provides a means to control the dynamics of the production process. (C) 2005 American Institute of Chemical Engineers.