the invention relates to a composition for the extension and increase of the activity of herbicidal compositions containing as herbicidally active ingredient at least one carbamate and / or thiolcarbamate and / or chloroacetanilide and / or dichloroacetanilide derivative and optionally antidotes therefore , which comprises at least one thio - or dithiophosphoric acid ester of the formula ## str1 ## wherein r stands for identical or different alkyl , alkenyl , isoalkyl , isoalkenyl , haloalkyl , haloalkenyl , isohaloalkyl or isohaloalkenyl groups , each containing up to 4 carbon atoms ; r &# 39 ; represents identical or different alkyl , alkenyl , isoalkyl , isoalkenyl , haloalkyl , haloalkenyl , isohaloalkyl , isohaloalkenyl groups , each containing up to 4 carbon atoms ; x is oxygen or sulfur , x 1 is oxygen or sulfur , with the proviso that at least one of the x 1 groups is other than oxygen .