- 14 - HOE 90/F 322 Process for the preparation of biaryls Process for the preparation of biaryls of the formula (1) R1m - Ar - Ar - R1m (1) wherein Ar is a phenylene or naphthylene radical, R1 is a hydrogen, fluorine or chlorine atom or an unbranched or branched alkyl(C1-C6)-, alkyl(C1-C6)-O-, alkyl(C1-C6)-CO- or alkyl(C1-C6)-SO2H radical and m is the number of still unsubstituted =C- positions on the Ar radical, in which a compound of the formula (2) R1m - Ar - X (2) wherein Ar, R1 and m have the meanings cited above and X is a chlorine or bromine atom, is dehalogenated and dimerized in the presence of a palladium catalyst on a support material, of a reducing agent, a hydrogen halide acceptor, a polyether or polyether mixture and of water at temperatures of about 50 to about 120.degree.C.