N-pyridinesulfonyl-N'-pyrimidinyl- and -triazinyl-ureas of formula I ##STR1## wherein R.sub.1 is hydrogen or fluorine; or R.sub.1 together with R.sub.3 is a C.sub.2 -C.sub.4 alkylene chain; R.sub.3 is hydrogen, fluorine or C.sub.1 -C.sub.3 alkyl; R.sub.2 is hydrogen, fluorine or C.sub.1 -C.sub.3 alkyl; R.sub.4 is hydrogen, fluorine, chlorine or C.sub.1 -C.sub.3 alkyl; R.sub.5 is hydrogen, fluorine, chlorine, C.sub.1 -C.sub.3 alkyl, or C.sub.1 -C.sub.3 alkyl substituted by fluorine or chlorine; R.sub.a is hydrogen or halogen, or a C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy or C.sub.1 -C.sub.4 alkylthio radical each of which may be unsubstituted or mono- or poly-substituted by halogen; R.sub.b is hydrogen or a C.sub.1 -C.sub.4 alkyl radical; X is C.sub.1 -C.sub.3 alkyl, C.sub.1 -C.sub.3 alkyl mono- to tri-substituted by halogen, C.sub.1 -C.sub.3 alkoxy, or C.sub.1 -C.sub.3 alkoxy mono- to tri-substituted by halogen; Y is halogen, C.sub.1 -C.sub.3 alkyl, C.sub.1 -C.sub.3 alkyl mono- to tri-substituted by halogen, C.sub.1 -C.sub.3 alkoxy, or C.sub.1 -C.sub.3 alkoxy mono- to tri-substituted by halogen, or is cyclopropyl, methylamino or dimethylamino; and E is nitrogen or the methine group, and the salts of those compounds, with the proviso that at least one of the radicals R.sub.1 to R.sub.5 is fluorine, or one of the radicals R.sub.4 and R.sub.5 is chlorine, have good selective-herbicidal properties. The preparation of those compounds and their use as herbicidal active ingredients is described.

Compounds of the formula XI, wherein R, R.sub.4, R.sub.8 and R.sub.38 are as defined in claim 1, are useful as intermediates in the preparation of compounds of formula I. Mixtures of a herbicidally effective amount of a pyridylsulfonylurea of formula I, ##STR1## wherein R, R.sub.1, R.sub.2 and A are as defined in the specification and of a herbicide-antagonistically effective amount of a sulfamoylphenylurea of formula II, ##STR2## wherein R.sub.7 to R.sub.11 and A.sub.2 are as defined in the specification are very suitable for controlling weeds in crops of useful plants, especially maize and sugar cane.