The high-temperature surface oxidation ofH 2 on a platinum catalyst in the presence of excess air has been studied over a range of surface temperatures from 450 to lif/0K and equivalence ratios from 0.05 to 0.20. The objectives were ( I ) to develop a system in which the surface kinetics of various fuel--air mixtures can be studied under conditions of interest to catalytic combustion1 and (2) to determine the high-temperature surface oxidation rate for lean H2/air mixtures on a platinum catalyst. The experimental system considered was the laminar boundary layer of a heated catalytic plate. Under all conditions investigated the surface reaction rapidly became diffusion limited downstream of the plate leading edge. A finite difference scheme was utilized to model numerically the flow field above the plate surface. This enabled surface reaction rate data to be obtained under those conditions where surface reaction rates were significantly influenced by transport effects. Based on a one-step model for H 2 oxidation the data were found to correlate well with a reaction rate expression of the form R s = 1.4 ร Io3[H2]sexp(-38501RT)(molelcm2s). The effects of heat and mass transfer on the kinetics a~ also discussed.