5-Amino-6-pyridazones of the general formulae Ia and Ib ##STR1## where R.sup.1 is C.sub.1 -C.sub.4 -alkyl which may carry up to three halogen atoms, R.sup.2 is C.sub.1 -C.sub.4 -alkyl or C.sub.3 -C.sub.6 -alkenyl, where these groups may carry up to two phenyl radicals, or C.sub.3 -C.sub.6 -alkynyl, A is --CO-- or --SO.sub.2 --, B is C.sub.1 -C.sub.6 -alkyl, C.sub.2 -C.sub.6 -alkenyl or C.sub.2 -C.sub.6 -alkynyl, where these groups may carry up to three of the following radicals: halogen, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -alkylthio and/or phenyl; an isocyclic or heterocyclic C.sub.3 -C.sub.7 -cycloalkyl group or an isocyclic or heterocyclic C.sub.3 -C.sub.7 -cycloalkenyl group, where these groups may be fused with one or two cycloalkyl groups of this type or with one or two benzene nuclei, where the total number of ring members is from 3 to 16 and these cyclic radicals may carry up to three of the following groups: halogen, C.sub.1 -C.sub.4 -alkyl, C.sub.2 -C.sub.6 -alkenyl, C.sub.2 - C.sub.6 -alkynyl and/or phenyl; a mononuclear to trinuclear aromatic or heteroaromatic radical which may carry up to three of the following groups: C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -haloalkyl, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -haloalkoxy, C.sub.1 -C.sub.4 -alkylthio, C.sub.1 -C.sub.4 -alkylsulfinyl, C.sub.1 -C.sub.4 -alkylsulfonyl, cyano, nitro, carbo-C.sub.1 -C.sub.4 -alkoxy, N,N-di-C.sub.1 -C.sub.4 -alkylcarbamido and/or halogen.These compounds are used as herbicidal active ingredients.