Substituted 5-trifluoromethyl-1,3,4-thiadiazol-2-yl-oxyacetic acid amides of the formula ##STR1## in which R.sup.1 and R.sup.2 are identical or different and each represent alkyl, alkenyl, alkinyl, alkoxy, aralkyl, cycloalkyl, cycloalkenyl or aryl, each of which is optionally substituted, or a nitrogen-containing heterocyclic radical, or, together with the nitrogen atom to which they are bonded, form an optionally substituted, optionally partially unsaturated and optionally benzo-fused monocyclic or bicyclic structure which optionally contains further hetero atoms, with the proviso that R.sub.1 does not represent methyl when R.sup.2 represents phenyl, which possess herbicidal activity.