Clean polycrystalline titanium surfaces were exposed at near-ambient temperatures to oxygen at pressures near 10−9 Torr and the oxidation process characterized by Auger electron spectroscopy, secondary emission changes, and by changes in the work function. A study was also made of the coadsorption of lead and oxygen. From the different behaviour of three different titanium Auger peaks during oxygen adsorption new information is obtained on the chemisorption of a subsurface monolayer of oxygen prior to the formation of thick oxide layers. Coadsorption with lead can produce an enhancement of the oxygen Auger signal which is ascribed to modifications in the location of the oxygen layer. The Auger spectra are also influenced by changes in electron transfer between the two metals and oxygen. Possible implications for the catalytic properties of metal particles on titanium oxides are pointed out.