Abstract: Process for the preparation of filled heat-curable compounds of the polyurethane type by reaction of condensation of the constituents of the desired compound in the presence of a pulverulent filler, which is characterized in that the said filler is predispersed in the presence of a stabilizing agent in a liquid organic phase compatible with the desired heat-curable compound in the course of its formation reaction, the said filler being then in the form of a homogeneous and stable suspension, and the suspension thus prepared is then introduced into the reaction mixture before, during or after the introduction of at least one of the constituents of the desired heat-curable compound.The process according to the invention makes it possible to produce compounds of the polyurethane type whose mechanical and physical characteristics are at least equivalent or even improved in relation to those of the unfilled identical compounds by virtue of the excellent distribution of the inorganic filler.