Response of steady-state photoconductivity to changes in oxygen partial pressure (10(-3) to 1 atm) has been quantitatively studied in thin-film polycrystalline TiO2:Nb and ZnO at 80-120 degrees C. The magnitude of photoconductivity varied as a square root of illumination intensity regardless of oxygen pressure. Both materials showed fast response to oxygen, although in different pressure ranges. Zinc oxide was more sensitive to lower oxygen pressures while titanium dioxide worked better at pressures close to 1 atm.