The oxidation of , , and has been studied at temperatures of 1300°–2000°K, and at oxygen partial pressures of 2–20 Torr. Below 1970°K, at oxygen pressures around 10 Torr, measurements of the rate of total oxygen consumption vs. time show an initial period of high linear rate, an intermediate region where the rate declines sharply with time, and a final plateau region of virtually zero oxidation rate. For each of the silicides, the total oxygen consumed prior to the attainment of the plateau decreases with temperature, and under given experimental conditions is largest for , less by a factor of about six for , and less by another factor of six for . The oxidized samples display a smooth glassy outer oxide layer that bridges across the tops of the cracks in the alloys and an inner oxidized zone, consisting of several irregular phases. Electron micro‐probe analysis and x‐ray photomicrographs of the oxidized specimens show that the outer protective oxide is pure , within the limits of detectability, i.e., the outer oxide contains less than 0.1% Mo. The inner oxide layer contains , molybdenum rich phases, including the terminal solid solution phase, and the original alloy phase. Evidence is presented that suggests that the oxide layers grow by inward diffusion of oxygen to the oxide/alloy interface where preferential oxidation of silicon occurs. The excellent oxidation resistance of the molybdenum silicides derives from the formation of this continuous layer of pure silica. Above 1970°K, at oxygen pressures above 10 Torr, an increased oxidation rate is observed due to formation of at the alloy/oxide interface, which causes rupture of the protective oxide. Below 1970°K, at oxygen pressures near 2 Torr, the rate of oxidation of is linear at all times since the oxygen partial pressure is insufficient to maintain a protective layer on the alloy surface.