The kinetics and morphology of the oxidation process of magnesium-aluminium oxynitride (MgAlON), aluminium oxynitride (AlON), 0' SiAlON-ZrO2, and BN-ZCM have been studied in the temperature range 1373-1773 K. Oxidation experiments with powder and plate samples of the above materials have been carried out in air. MgAlON shows the best resistance to oxidation at lower temperatures (<1473 K), whereas at higher temperatures (similar to 773 K), AlON shows the best resistance. O'SiAlON-ZrO2 shows very good oxidation resistance up to 1673 K. But its oxidation rate increases strongly above 1673 K, presumably due to the formation of liquid phase. BN-ZCM has the poorest oxidation resistance due to the evaporation of B2O3. The activation energies for the chemical oxidation reaction of AlON, MgAlON, and O'SiAlON-ZrO2 are 214, 330 and 260 kJ/mol, respectively. The overall diffusion activation energies for AlON, MgAlON, O'SiAlON-ZrO2 and BN-ZCM are 227, 573, 367 and 289 kJ/mol, respectively.