A method for studying the heat resistance of composite aluminum nitride-based ceramic materials in air at 1073 - 1273 K is developed that allows the change in mass to be measured with an accuracy of 0.15 - 0.17 mg. The interaction between AIN-based composite materials and a phosphate binder (H3PO4) is studied and compared with hot-pressed specimens. A mechanism for the effect of the binder on the kinetics of oxidation is proposed. The relatively low activation energies (152 and 205 kJ/mole) suggest that the oxidation process is mainly determined by the diffusion of aluminum ions through the alpha-Al2O3 film.