A process for preparing a filled polymer extrudate, with which a flowable composition is made, composed of a carrier fluid and reinforcing agents or filler material (9), or coloring pigments (12 added to them in a first extruder (2) and a polymer melt of a thermoplastic polymer (16) in a second extruder (14, in which the composition and the polymer melt are subsequently co-extruded in a co-extruding step in such a way that the polymer melt encloses the composition forming the core of the generated extrudate strand (22).