Thermal oxidation of sputter-deposited indium nitride films has been investigated in air at the heating rate of 10-degrees-C min-1. Surface oxidation occurred at 300-350-degrees-C and many domes were formed. Complete formation of In2O3 occurred with a drastic increase in the resistivity at 400-500-degrees-C when the domes were destroyed. Formation and destruction of the domes is explained by the volume increase from the nitride to the oxide. The oxidized films are sensitive to water vapour and ammonia.