The present invention relates to substituted 1,2,5-oxadiazole compounds of the formula I and the N-oxidesand salts thereof and to compositions comprising the same. The invention also relates to the use of the 1,2,5-oxadiazole compounds or of the compositions comprising such compounds for controlling unwanted vegetation. Furthermore,the invention relates to methods of applying such compounds. In formula I, the variables have the following meanigns R is e.g. hydrogen, cyano, nitro, halogen, C1-C6--alkyl, C3-C7-cycloalkyl, C3-C7- cycloalkyl-C1-C4-alkyl, C1-C6-haloalkyl, C2-C6-alkenyl, C2-C6-haloalkenyl, C2-C6-alkynyl,C2-C6-haloalkynyl, C1-C4-alkoxy-C1-C4-alkyl,C1-C4-haloalkoxy-C1-C4-alkyl,O-Ra, Z-S(O)n-Rb, Z-C(=O)-Rc, Z-C(=O)-ORd, Z-C(=O)-NReRf, Z-NRgRh, Z-phenyl and Z-heterocyclyl etc; R1 ise.g. Z1-cyano, halogen, nitro, C1-C8-alkyl, C2-C8-alkenyl, C2-C8-alkynyl,C1-C8-haloalkyl, C1-C8-alkoxy, C1-C4-alkoxy-C1-C4-alkyl, Z1-C1-C4-alkoxy-C1-C4-alkoxy, C1-C4-alkylthio-C1-C4-alkyl, Z1-C1-C4-alkylthio-C1-C4-alkylthio, C2-C6-alkenyloxy, C2-C6-alkynyloxy, C1-C6-haloalkoxy, C1-C4-haloalkoxy-C1-C4-alkyl, Z1-C1-C4-haloalkoxy-C1-C4-alkoxy, Z1-S(O)k-R1b, Z1-phenoxy and Z1-heterocyclyloxy;R2,R3 are identical or different and e.g. hydrogen, halogen, Z2-OH, Z2-NO2,Z2-cyano,C1-C6-alkyl, C2-C8-alkenyl, C2-C8-alkynyl, Z2-C3-C10-cycloalkyl, Z2-C3-C10-cycloalkoxy, C1-C8-haloalkyl, Z2-C1-C8-alkoxy, Z2-C1-C8-haloalkoxy, Z2-C1-C4-alkoxy-C1-C4-alkoxy, Z2-C1-C4-alkylthio-C1-C4-alkylthio, Z2-C2-C8-alkenyloxy, Z2-C2-C8-alkynyloxy, Z2-C1-C8-haloalkoxy, Z2-C2-C8-haloalkenyloxy, Z2-C2-C8-haloalkynyloxy, Z2-C1-C4- haloalkoxy-C1-C4-alkoxy, Z2-(tri-C1-C4-alkyl)silyl, Z2-S(O)k-R2b, Z2-C(=O)-R2c, Z2-C(=O)-OR2d, Z2-C(=O)-NR2eR2f, Z2-NR2gR2h, Z2a-phenyl and Z2a-heterocyclyl; R4 is selected from the group consisting of hydrogen, halogen, cyano, nitro, C1-C4-alkyl and C1-C4-haloalkyl; R5 is selected from the group consisting of hydrogen, halogen, C1-C4-alkyl and C1-C4-haloalkyl; provided that at least one of the radicals R4 and R5 is different from hydrogen; n is 0, 1 or 2; k is 0, 1 or 2.