The oxidation of a cermet composed of nickel ferrite (Ni-x-Fe3-xO4), nickel oxide (NiyFe1-yO), and Ni-Cu alloy (Cu-z-Ni1-z)(with x = 0.8, y = 0.84, and z = 0.44) has been studied by thermogravimetry, at 960 degrees C, under controlled oxygen partial pressure. The rate of oxidation increases with the oxygen partial pressure up to 5.1 x 10(3) Pa, then it becomes independent of the oxygen pressure. This is due to the presence of the two copper oxides, CuO and Cu2O, above this oxygen pressure. Scanning electron microscopy observation of oxidized samples has shown that the oxidation mechanism involves both external and internal oxidation.