The oxidation of zinc in air at 294 K has been studied for exposure times from 1 min to 150 h. The fraction of zinc in the Zn+2 valence state has been determined by high resolution Auger electron spectroscopy. Surface oxide thickness was measured by using AES with argon ion sputter etching. The adsorbed oxygen was shown by x-ray photoelectron spectroscopy to be in two states, one corresponding to O−2 in ZnO, the other being chemisorbed oxygen. The two O1s photoelectron peaks were partially resolved by means of a van Cittert-type deconvolution calculation and the relative separation was found to be 1.7 eV, in agreement with that for low level O2 adsorption of polycrystalline zinc under UHV conditions.1 The effect of temperature was also determined in the range of 294–573 K. The fraction of zinc in the Zn+2 valence state after 1 h exposure was found to increase nearly linearly with temperature, with ZnO formation complete at 573 K.