The process for the production of an alloy of cross-linked or partially cross-linked rubbers and aromatic polyesters basically consists of reacting a mixture of a rubber latex and an aqueous solution of an alkali metal or alkaline earth metal diphenolate with a solution of a dicarboxylic acid halide and/or a carbonyl halide in a water-immiscible solvent. An aromatic polyester forms at the water/organic solvent phase boundary and goes over into the organic phase. At the same time, the rubber migrates from the aqueous into the organic phase. When the organic phase is separated and the organic solvent removed, the alloy of rubber and oirganic polyester remaining behind is suitable for the production of moulded articles of all kinds.