A novel spatiotemporal perturbation method for nonlinear surface reactions is reported, thus allowing the creation of new spatially localized structures. Forcing was achieved by dosing reactant gases through a capillary positioned near the catalyst surface, providing control over the local surface coverage and reaction rate. The emergence of localized concentration patterns and oscillations in an otherwise stable System is attributed to a local modification of the catalytic propel-ties of the surface due to external forcing. Based on the spatial orientation, the temporal and thermal stability of the modified surface, as well as the affinity of CO toward the Perturbed surface, subsurface O is proposed as a possible source of the observed localized patterning and surface memory effect. (C) 2008 American Institute of Chemical Engineers AIChE J, 55: 172-179,2009