The oxidation of the amorphous Pd78Au4Si18 alloy aged at temperatures of 150 to 300 °C for 1 to 20 days is investigated using Auger electron spectroscopy and ion‐beam etching. Samples are characterized by x‐ray diffraction and electrical contact resistance at each aging stage. Partially crystallized samples as well as pure palladium samples also are evaluated for comparison. Oxidation is controlled by the inward diffusion rate of oxygen for both the alloy and elemental Pd samples. The oxygen front for the alloy is deeper than that for Pd. Oxygen depth profiles for Pd samples decline monotonically and gradually, but for the alloy they have up to three plateaus. The composition in each plateau zone is analyzed by studying the Si‐LVV Auger spectrum. Partial crystallization prior to the oxidation has little effect on the oxidation rate of the alloy. Even with an apparent oxide layer 90 Å thick, the alloy shows little increase in resistance. This could be explained by nonuniformities in the layer.