The oxidation, by O2 and N2O, of evaporated metal films of Nb, Ta, and Ti has been studied in the temperature range 195-473 K. Fast dissociative adsorption of N2O, which was accompanied by N2 evolution, occurred on all the three metals at 195 K. At the latter temperature, some incorporation also occurred on Ti film, but the amount adsorbed on Nb was below that required to saturate the film surface with oxygen atoms. Oxygen adsorption on all three metals also took place rapidly at 195 K and the metals showed in general more tendency for oxygen adsorption through O2 than N2O. At temperatures ?303 K, the oxidation reaction took place by either O2 or N2O with each film at a rate which depended both on the pressure of the reacting gas and the temperature of the metal film. The Ti film was the most, and Nb the least, active of the three metals for O2 or N2O oxidation. Both the activation energy (E) and the preexponential factor (A) increased as the extent of oxidation (X or Y) of each film increased so that the experimental rate remained almost constant, suggesting the operation of a compensation effect in the oxidation of the three films. The effect was likely to arise from a relationship between the heat and the entropy of adsorption, leading to a compensation between activation energy and entropy of activation (and hence the preexponential factor). Values of A and E were lower for O2 adsorption on each film than for N2O and this was ascribed to the higher heat of oxygen adsorption as compared with that of N2O. On the other hand, values of A and E for the Ti film were in general smaller than the corresponding values for Ta and Nb films, such data are in parallel with the greater ease with which the oxidation of the Ti film occurred in comparison with the other two films.