The kinetics of CO oxidation and NO reduction reactions over alumina and alumina-ceria supported Pt, Rh and bimetallic pt/Ph catalysts coated on metallic monoliths were investigated using the step response technique at atmospheric pressure and at temperatures 30-350 degrees C. The feed step change experiments from an inert flow to a flow of a reagent (O-2, CO, NO and H-2) showed that the ceria promoted catalysts had higher adsorption capacities, higher reaction rates and promoting effects by preventing the inhibitory effects of reactants, than the alumina supported noble metal catalysts. The effect of ceria was explained with adsorbate spillover from the noble metal sites to ceria. The step change experiments CO/O-2 and O-2/CO also revealed the enhancing effect of ceria. The step change experiments NO/H-2 and H-2/NO gave nitrogen as a main reduction product and N2O as a by-product. Preadsorption of NO on the catalyst surface decreased the catalyst activity in the reduction of NO with H-2. The CO oxidation transients were modelled with a mechanism which consisted of CO and O-2 adsorption and a surface reaction step. The NO reduction experiments with H-2 revealed the role of N2O as a surface intermediate in the formation of N-2. The formation of N-N bonding was assumed to take place prior to, partly prior to or totally following to the N-O bond breakage, High NO coverage favors N2O formation. Pt was shown to be more efficient than Ph for NO reduction by H-2.