Abstract: Apparatus for kneading compounded resinous material includes a cylinder within which there is sequentially arranged a preheating feed zone, a plasticizing kneading zone, a degassing zone and a measuring zone. A screw is rotatably positioned within the cylinder and extends through all of the afore-mentioned zones. The portion of the screw within the plasticizing kneading zone has a plurality of continuous helical flights each of which is given a front wall facing in the direction of screw rotation substantially perpendicular thereto. A rear portion of each flight defines a groove with the next adjacent flight such that the diameter of the screw between flights progressively decreases in the direction opposite to screw rotation. A plurality of axially extending recesses are formed on the interior surface of the cylinder which extend at least through the preheating feed zone and the plasticizing kneading zone.