Experimental kinetic data have been obtained for the CO oxidation reaction over laboratory made platina-rhodium monolithic catalyst. Inert layers ofy-yalumina were deposited over the active layer in order to elucidate the diffusional effects on the monolithic catalyst. A synthetic gas mixture consisting of CO1, O2and N2was the feed of an integral tubular reactor between 180 and 370°C. A first order kinetic rate expression with respect to CO concentration, which includes an inhibition term of second order was found to fit the experimental data via a model which also accounts for diffusional resistances. The obtained kinetic and diffusional data can be used in the design of a catalytic converter with improved efficiency. The results can also be used to interpret the diffusion mechanism inside the catalyst itself and it was concluded that Knudsen diffusion mechanism prevails.