The invention relates to novel reactive dyes of the formula ##STR1## wherein Z is --NH.sub.2, C.sub.1 -C.sub.6 alkylamino, N,N--di(C.sub.1 -C.sub.6)alkylamino, cyclohexylamino, N--(C.sub.1 -C.sub.6)alkyl-N-cyclohexylamino, N,N-dicyclohexylamino, phenyl(C.sub.1 -C.sub.2)alkylamino, N--(C.sub.2 -C.sub.4)alkyl-N-phenylamino, naphthylamino, a heterocyclic radical which is bound through an amino group and which may contain further fused carbocyclic rings, or a radical which is bound through the nitrogen atom of an N-heterocyclic ring and which may contain further hetero-atoms, and wherein the alkyl and cyclohexyl moieties, phenyl and naphthyl rings and heterocyclic radicals may be further substituted, and one Y is hydrogen and the other is sulfo. Strong red dyeings and prints are obtained with these dyes on cellulose fibres.