A process for preparing alkenylhalosilanes by reacting alkenyl halide in the gas phase in a reactor comprising a reaction tube (1) equipped with an inlet (2) at one end of the tube and with an outlet (3) at the other end of the tube, and having a gas inlet device (4) having a plurality of gas feed points (5) that are spaced apart in the direction of the longitudinal axis of the reaction tube (1) and open into the reaction tube (1). The process permits the preparation of alkenylhalosilanes in high yield and with high selectivity. The formation of soot is distinctly lower compared to conventional reactors.