The chlorination kinetics of tungsten, molybdenum, and three of their binary alloys have been studied as part of a Bureau of Mines effort to provide information of value when considering chlorine metallurgy processes. Tungsten and molybdenum were used for this initial investigation of alloys because they are chemically similar, form a complete range of solid solutions, and have been shown to chlorinate at temperatures sufficiently different so as to facilitate the determination of temperature dependency of reactivity by experiments based on the measurement of weight loss as the volatile chlorides are formed. Both the pure metals and alloys containing 22, 48, and 72 atomic percent (a/o) molybdenum were found to chlorinate between 400 deg and 775 deg c at rates of 10-7 to 10-5 mole per square centimeter per minute, with the reaction rate dependent upon the 0.6 Power of chlorine pressure. Molybdenum exhibited the highest reactivity, tungsten was the least reactive, and the alloys showed intermediate reactivity with respect to temperature. Single crystals of the pure metals showed marked anisotropy upon chlorination. When chlorinated, the polycrystalline alloy specimens of 22 and 72 percent molybdenum tended to show the crystalline anisotropy exhibited by the major component, while the 48 percent molybdenum specimen developed no pattern similarity to the pure metals.