3-(4-Cyanophenyl)uracils of the formula I wherein A is hydrogen, methyl or amino; Y is oxygen or sulfur; R1 is hydrogen or halogen; R2 is hydrogen, halogen, alkyl, haloalkyl, alkylthio, alkylsulfenyl or alkylsulfonyl; R3 is hydrogen, halogen or alkyl; R4 is hydrogen, haloalkyl; or unsubstituted or substituted alkyl, cycloalkyl, alkenyl, alkynyl, alkylcarbonyl, alkenylcarbonyl, alkynylcarbonyl or alkylsulfonyl, methods and intermediates for their manufacture, and their use as herbicides or for the desiccation or defoliation of plants.