The invention describes a novel process for the preparation of polycarbonate and/or polyarylate block copolymers with poly(aryl ethers). The process is comprised of the steps:(a) the reaction of a dihydroxy-terminated poly(aryl ether) oligomer with a high molecular weight polycarbonate, or a high molecular weight polyarylate, or a high molecular weight poly(arylate-carbonate) to yield a block copolymer; followed by(b) the coupling of the material obtained in step (a) to the required molecular weight, using a diaryl ester of carbonic acid or of a dicarboxylic acid.Both steps are performed in the presence of a catalyst. The copolymerizations can be run in bulk under vacuum in a single or twin screw extruder. Using the above conditions high molecular weight, high quality block copolymers having a combination of excellent properties are obtained in a matter of minutes.