Oxime esters of substituted quinoline-8-carboxylic acids of the formula ##STR1## where X is hydrogen, C.sub.1 -C.sub.4 -alkyl or halogen, Z is hydrogen or methyl, R.sup.1 is C.sub.1 -C.sub.6 -alkyl, C.sub.1 -C.sub.4 -alkoxymethyl, C.sub.1 -C.sub.4 -alkoxyethyl, C.sub.1 -C.sub.4 -alkylthiomethyl, C.sub.1 -C.sub.4 -alkylthioethyl, C.sub.1 -C.sub.4 -alkoxycarbonyl, C.sub.3 -C.sub.6 -alkenyl or C.sub.5 -C.sub.8 -cycloalkyl, each of which is unsubstituted or bears up to 3 methyl substituents, hydrogen, cyano, acetyl, benzoyl, unsubstituted benzyl or phenyl, or benzyl or phenyl bearing up to 3 substitutents selected from the group consisting of halogen, cyano, trifluoromethyl, C.sub.1 -C.sub.4 -haloalkyloxy, C.sub.1 -C.sub.6 -alkylthio, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -alkyl, hydroxy, dimethylamino or acetamino, R.sup.2 is hydrogen if R.sup.1 is not hydrogen, R.sup.2 further denotes C.sub.1 -C.sub.6 -alkyl, C.sub.1 -C.sub.4 -alkoxymethyl, chloromethyl, azolylmethyl, 1,1-dimethoxymethyl, cyano, C.sub.1 -C.sub.4 -alkoxycarbony, C.sub.1 -C.sub.4 -alkoxy, phenyl if R.sup.1 is H, CH.sub.3 or acetyl, or R.sup.2 denotes, when R.sup.1 is H or methyl, furyl, tetrahydrofuryl, thienyl, tetrahydropyranyl, tetrahydrothiopyranyl, dihydro-.DELTA..sup.3 -pyranyl or dihydro-.DELTA..sup.3 -thiopyranyl; further, R.sup.1 and R.sup.2, together with the carbon atom to which they are linked, denote C.sub.1 -C.sub.12 -cycloalkylidene, C.sub.5 -C.sub.6 -cycloalkenylidene or 4-oxacyclohexadienylidene, each of which is unsubstituted or bears up to 3 methyl substituents, it being possible, where the ring is 5-membered or 6-membered, or doubly unsaturated 6-membered, for it to contain an oxygen or sulfur atom, their preparation, and their use as herbicides.