Abstract: A lightweight pyrogen igniter assembly including an elongated molded plastic tube adapted to contain a pyrogen charge and to be inserted into a rocket motor casing for ignition of the rocket motor charge with a molded plastic closure cap provided for the elongated tube and including an ignition charge within the cap for igniting the pyrogen charge and an electrically actuated ignition squib within the cap for igniting the ignition charge. The ignition charge is contained within a portion of the closure cap and it is retained therein by a noncorrosive ignition pellet retainer or screen which is adapted to rest on a shoulder of the elongated tube when the closure cap and tube are assembled together. The interior of the closure cap and the exterior of the elongated tube are provided with matching tapered spiral buttress threads to serve as the attachment means therefor.