We have studied the kinetics of magnetite oxidation in O2-bearing atmospheres in the presence of electromagnetic radiation. No perceptible oxidation of magnetite by ultraviolet (UV) photostimulation occurred. These results do not corroborate previous conclusions by Huguenin (1973a,b; 1974) as to the occurrence of this process. Therefore, although we cannot totally rule out the possibility that the process actually occurs, we conclude that there is not yet a basis in laboratory experiments for inferring that UV photostimulated oxidation of magnetite occurs naturally on the surface of Mars.