We report experimental and computational studies of reaction dynamics on Pt/Rh and Pt/TiO2 microcomposite catalytic surfaces. Reaction fronts initiated at the material interface dominate both steady and dynamic behavior of the composite catalytic material. Our analysis links the transient phenomenon of front initiation to the bifurcations of reaction-diffusion systems with active boundaries. (C) 2001 Published by Elsevier Science B.V.