In order to prepare thermoplastic molding materials from pulverulent polyphenylene ethers and aromatic vinyl polymers by melt extrusion, the pulverulent polyphenylene ether is first of all compacted and/or sintered under pressure and if necessary with the addition of heat, preferably under a pressure corresponding to a nip pressure of from 1 to 100 kN/cm, to form a porous compact. The compact is then fed in the form of agglomerates having a particle size of from about 0.5 mm to about 20 mm into an extruder or the like, mixed with the aromatic vinyl polymer and if desired further components, and melted. In this way the proportion of the fines in the polyphenylene ether is considerably reduced, with the result that there is virtually no further danger of dust explosions. Further advantages include improved ease of metering and reduced electrostatic charge of the agglomerates. The extruded molding materials have good mechanical properties and also high thermal stability.