The temperature-programmed reduction of three Pd-Cu/KL-zeolite bimetallic catalysts has been studied using X-ray absorption near edge spectroscopy (XANES) and infrared spectroscopy with the probe molecule CO. We show that complete alloying with electronic perturbation of both components (with respect to their metallic state) is reached over the full range of compositions analyzed. It is also shown that the effect of reduction temperature on the nature of the surfaces exposed by the active phases, as well as the sintering processes, is primarily governed by the Pd:Cu ratio.