Novel 3-aryl-2-halothiopropionic acid compounds of the formula ##STR1## wherein X is chlorine or bromine,R.sup.1 is hydrogen, a salt-forming cation, an aliphatic radical or a substituted aliphatic radical wherein the substituent is halogen, haloalkyl, hydroxy, alkoxy, alkoxy-carbonyl or aryl,R.sup.2 is hydrogen, halogen or alkylR.sup.3 is hydrogen or alkyln is an integer from 0 to 3; andR.sup.4 is halogen, alkyl, haloalkyl or nitro and wherein the radical R.sup.4, when n is 2 or 3, may be the same or different,Are outstandingly effective herbicides, exhibiting particularly selective action.