Cationic azo dyestuffs of the formula ##STR1## wherein X.sup.(+) denotes an ammonium group, m denotes 0 or 1,R denotes hydrogen, halogen, C.sub.1 - to C.sub.4 -alkyl, C.sub.1 - to C.sub.4 -alkoxy, hydroxyl, amino, sulphonamido and carboxamido, or acylamino which is optionally substituted by halogen or a quaternary group, R.sup.1 denotes hydrogen, C.sub.1 - to C.sub.4 -alkyl, halogen or C.sub.1 - to C.sub.4 -alkoxy,R.sub.2 and R.sub.3 independently of one another denote hydrogen, C.sub.1 - to C.sub.4 -alkyl, C.sub.1 - to C.sub.4 -alkoxy or acylamino, andAn.sup.(-) denotes an anion, andwherein the azo group and hydroxyl group of ring a are located adjacent to one another and further carbocyclic or heterocyclic rings can be fused to ring a, are used for dyeing paper.