A process for producing a solid dispersion of an active ingredient which comprises feeding the active ingredient and a matrix-forming agent to an extruder and forming a uniform extrudate, wherein the extruder comprises at least two rotating shafts (2), each of the shafts (2) carrying a plurality of processing elements disposed axially one behind the other, the processing elements defining (i) a feeding and conveying section (R； A), (ii) at least one reverse-flight section (D), and (iii) a discharging section (E), wherein the processing elements defining the reverse-flight section (R； D) comprise at least one reverse-flight element (14) which is based on a screw-type element having a conveying direction being opposite to the general conveying direction of the extruder.
