1. We investigated the kinetics and mechanism of oxidation of low-alloy molybdenum and molybdenum-tungsten alloys in air at 400–1100°. 2. Alloying of molybdenum with tungsten increases its resistance to oxidation up to 600–700° at higher temperatures (800–1100°) the favorable effect of tungsten is suppressed by intensive evaporation of MoO3. 3. The addition of carbon increases with oxidation rate due to formation of gaseous CO and CO2, which disrupt the continuity of the oxide film. Small additions of zirconium and titanium have practically no effect on the oxidation rate of the alloys above 600°. At lower temperatures titanium reduces, and zirconium increases, the oxidation rate of molybdenum.