Substituted sulfonylureas of the formula I ##STR1## where the substituents and indices have the following meanings: X is oxygen or sulfur;Z is nitrogen or methine (.dbd.CH--);R.sup.1 is halogen or substituted or unsubstituted C.sub.1 -C.sub.4 -alkoxycarbonyl or C.sub.1 -C.sub.3 -alkoxy, or a radical --CONR.sup.6 R.sup.7, whereR.sup.6 is hydrogen, C hd 1-C.sub.8 -alkyl or C.sub.1 -C.sub.6 -alkoxy andR.sup.7 is hydrogen or C.sub.1 -C.sub.8 -alkyl;R.sup.2 is halogen or substituted or unsubstituted C.sub.1 -C.sub.4 -alkoxy or C.sub.1 -C.sub.4 -alkyl;R.sup.3 is C.sub.1 -C.sub.4 -alkyl, C hd 1-C.sub.4 -alkylthio, C hd 1-C.sub.4 -haloalkyl, C.sub.1 -C.sub.4 -haloalkoxy, C.sub.1 -C.sub.4 -haloalkylthio, halogen, cyano, nitro, amino, mono-C.sub.1 -C.sub.4 -alkylamino, di-C.sub.1 -C.sub.4 -alkylamino, C hd 2-C.sub.6 -alkenyl, C.sub.1 -C.sub.4 -alkoxycarbonyl, C.sub.1 -C.sub.4 -alkanoyl or benzyl; a 5- or 6-membered saturated heterocycle which is attached by its nitrogen atom and which, besides methylene and a nitrogen, may also contain an oxygen or a sulfur atom; or, bonded to adjacent ring positions, --OCRR'O--, where R and R' are each hydrogen or C.sub.1 -C.sub.4 -alkyl;R.sup.4 is hydrogen or C.sub.1 -C.sub.4 -alkyl;R.sup.5 is halogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -alkylthio or C.sub.1 -C.sub.4 -haloalkyl;m is from 0 to 3 or, when R.sup.3 is halogen, from 0 to 5, differences among the R.sup.3 radicals being possible when m is 2 or 3; andn is from 0 to 2, a difference between the R.sup.5 radicals being possible when n is 2;and environmentally acceptable salts thereof, processes for their manufacture, and their use as herbicidal agents.