Abstract: Improved yields of monohydrogentrihalosilanes are achieved by contacting the residual silicon obtained from the preparation of organohalosilanes by a metal-catalyzed direct process by contacting the residual silicon simultaneously with gaseous hydrogen halide and with gaseous alkyl halide to form a residual silicon contact mass; selecting a temperature between about 200.degree. C. and about 350.degree. C. at which alkylation of the silicon contact mass in inhibited and at which hydrohalogenation of the silicon contact mass occurs; and heating the silicon contact mass at the selected temperature. The silicon reacts with the gaseous alkyl halide and the gaseous hydrogen halide at the selected temperature to produce improved yields of the monohydrogentrihalosilane.