The oxidation in air of substoichiometric films of SiOxby scanned, cw laser irradiation at 500 nm has been studied as a function of incident power density up to a maximum of 5.3 MW/cm2. Results obtained on substrates having widely different thermal conductivities suggest that the oxidation is thermally stimulated. Observed Auger electron spectra and measured refractive indices in oxidized films are characteristic of amorphous SiO2.