Abstract: An improved process for incorporating glass fibers into a thermoplastic synthetic resin wherein the glass fibers are continuously mixed with a molten thermoplastic synthetic resin and the resulting mixture is shaped into a desired article, involves preheating the glass fibers to a temperature not more than the melting point of the synthetic resin, feeding the preheated glass fibers and the molten synthetic resin separately to a premixing chamber, intermixing the resin and fibers within the chamber and thereafter introducing the resultant premix continously and directly into a two-stage degasifying screw-type extruder for effecting further homogenization of the premix and for extruding the desired article. The two-stage degasifying screw-type extruder used for carrying out this process is provided with a screw having a constant screw pitch in the two stages and in each stage with a low pressure zone and a high pressure zone in succession.