A 4,5-dichloro-imidazole-1-carboxylic acid aryl ester of the formula ##STR1## in which X represents trifluoromethyl, cyano or a group ##STR2## in which R.sup.1 represents a saturated or unsaturated aliphatic radical, which can be carrying one or more substituents selected from halogen, alkoxy with 1 to 6 carbon atoms and alkylmercapto with 1 to 6 carbon atoms, R.sup.2 represents hydrogen, alkyl with 1 to 8 carbon atoms, alkenyl with up to 8 carbon atoms or the formyl group, R.sup.3 represents alkyl with 1 to 8 carbon atoms or alkenyl or alkynyl each with up to 8 carbon atoms, it being possible for each of these alkyl, alkenyl and alkynyl radicals to carry one or more substituents selected from alkoxy with 1 to 4 carbon atoms, alkylmercapto with 1 to 4 carbon atoms, phenyl (which may optionally carry one or more substituents selected from halogen, alkyl with 1 to 4 carbon atoms, trifluoromethyl and alkoxy with 1 to 4 carbon atoms), furyl or thienyl, or represents cycloalkyl with 5 to 7 carbon atoms in the ring which is optionally substituted by alkyl with 1 to 6 carbon atoms, or represents phenyl which may optionally carry one or more substituents selected from halogen, alkyl with 1 to 4 carbon atoms, alkoxy with 1 to 4 carbon atoms, alkylmercapto with 1 to 4 carbon atoms and trifluoromethyl, or R.sup.2 and R.sup.3 conjointly with the adjoining nitrogen atom form an optionally substituted 5-membered to 7-membered heterocyclic radical in which 1 to 3 ring members may be selected from oxygen, sulfur and nitrogen, Y represents halogen, alkyl with 1 to 6 carbon atoms, trifluoromethyl, alkoxy with 1 to 6 carbon atoms, nitro, cyano or a ##STR3## group, in which R.sup.4 represents alkyl with 1 to 6 carbon atoms and n represents 0, 1, 2, 3, 4 or 5 which possesses plant protection properties especially herbicidal and plant growth regulant properties.