A kinetics study of the CO + NO reaction over Pd has been carried out using single-crystal, model planar-supported, and conventional high-surface-area Pd/Al2O3 catalysts. A pronounced structure sensitivity is evident that results in a rate enhancement over the Pd(111) single crystal relative to the more open (100) and (110) faces, and for larger supported particles relative to smaller ones. Temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) data indicate that the Pd(100) face is more active for NO dissociation and atomic N stabilization than the close-packed (111) plane. Similarly, TPD results show that smaller particles in the model supported catalysts are more active for atomic N formation and stabilization. The inverse correlation between reaction activity and N, formation and stabilization suggests that an inactive atomic N species plays a role in determining the reaction rate.