The throughput characteristic of a screw feeder and of a high-pressure roller mill equipped with it are investigated with four quartz materials 100/400 mu m, -400 mu m, -100 mu m, -20 mu m. The feeder throughput is proportional to the screw speed and does not depend on the counter-pressure created by varying the outlet resistance. The mill throughputs at different roller velocities line up to a proportionality to the screw speed. The screw speed has to exceed a lower limit to ensure a proper mill operation. This limit depends on the feed fineness. A screw feeder can increase the throughput by a factor 2 at the same roller velocity. The additional power draft can be kept smaller than 10% of the total power as the screw speed is adjusted properly.