Some controversy exists as to whether the reaction of oxygen and Si at the Si‐SiO2interface involves both atomic and molecular oxygen. From the direction of curvature of Arrhenius plots for the observed rate constants substantial support is obtained for the mechanism with two oxidant species. The direction of curvature was obtained from the second derivative of In kobswith respect toT−1. Parallel rate processes yield concave upwards Arrhenius plots while consecutive processes yield concave downwards plots.