Abstract: A continuous flow chemical laser is described in which chlorine dioxide and nitric oxide are reacted to produce atomic chlorine and hydrogen iodide is then introduced into the flow stream to form hydrogen chloride in an excited state. The hydrogen chloride may itself be lased in a transverse flow laser or carbon dioxide may be introduced which may be lased in a longitudinal or transverse flow laser. The required chlorine dioxide may be generated by passing chlorine and helium or another inert gas through loosely packed sodium chlorite. The nitric oxide may be introduced in two successive steps first to yield chlorine monoxide and in the second stage to yield atomic chlorine. The latter reaction facilitates operation in the supersonic transverse flow mode in which the hydrogen iodide and second injection of nitric oxide are made just as the flow stream is being transformed from a subsonic flow rate to supersonic flow rate.