The invention relates to novel substituted phenyluracils of general formula (I), in which: n = 0, 1 or 2; R1 = H, NH2 or optionally substituted alkyl, R2 = carboxy, cyano, carbamoyl, thiocarbamoyl or optionally substituted alkyl or alkoxycarbonyl; X = hydroxy, mercapto, amino, nitro, cyano, carboxy, carbamoyl, thiocarbamoyl, halogen, or optionally substituted alkyl, alkoxy, alkylthio, alkylsulphinyl, alkylsulphonyl, alkylamino, dialkylamino, alkylcarbonyl, alkoxycarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkylcarbonyloxy, alkoxycarbonyloxy, alkylaminocarbonyloxy, dialkylaminocarbonyloxy, phenylcarbonyloxy, alkylcarbonylamino, alkoxycarbonylamino, alkylsulfonylamino, alkenyl, alkenyloxy, alkenyloxycarbonyl, alkinyl, alkinyloxy or alkinyloxycarbonyl. In the case where n > 1, X, in the individual possible compounds, may have multiple given meanings.