The invention relates to a process for preparing sulphonyl-ureas of the general formula (I) ##STR1## wherein Ar.sub.1 represents a phenyl, naphthyl or thienyl group, the derivatives thereof substituted by C.sub.1-4 alkyl, C.sub.1-4 haloalkyl, (halo)alkoxycarbonyl, (halo)alkyloxy, nitro, cyano groups as well as by halogen atoms,Ar.sub.2 represents a phenyl, pyridyl, pirimidinyl or triazinyl group and the derivatives thereof substituted by C.sub.1-4 (halo)alkyl, C.sub.1-4 (halo)alkyloxy, amino, O-acyl, O-arylsulphonyl, O-(substituted carbamoyl) groups as well as by halogen atoms.According to the invention N-halogen aryl sulphonamidate is reacted in the presence of a carbonylating catalyst, carbon monoxide and an aromatic amine, optionally in the presence of a phase transfer catalyst, or N-halogen aryl sulphonamidate is reacted with carbon monoxide in the presence of a carbonylating catalyst, and optionally in the presence of a phase transfer catalyst, then the obtained reaction mixture is further reacted with an aromatic amine or an N-halogen-arylamine-alkali metal salt is reacted with aryl-sulphonamid in the presence of a carbonylating catalyst, carbon monoxide and optionally in the presence of a phase transfer catalyst or an amine, amine dihalogenid, aryl sulphonamid are reacted in the presence of a carbonylating catalyst and carbon monoxide and the obtained reaction mixture is worked up in a known manner.The thus prepared sulphonyl-ureas are biologically active compounds, which are used in the pharmaceutical industry and for regulating plant growth.