Abstract: Azo dyestuffs devoid of carboxylic acid and sulphonic acid groups and of the formula (I) ##STR1## wherein R is a hydrogen atom, halogen atom, cyano, nitro, hydroxy or amino group or an organic radical, R.sup.1 is a hydrogen atom, an optionally substituted hydrocarbon or heterocyclic radical or an amino group which may be substituted, Y is a group --OCOR.sup.2, --OSO.sub.2 R.sup.2 or --NHSO.sub.2 R.sup.2 wherein R.sup.2 is optionally substituted alkyl or aryl, K.sym. is a cationic group, X.crclbar. is an anion and the ring A may carry further substituents or have a benz ring fused thereon. Manufacture of such dyestuffs and use in the dyeing of synthetic polymeric materials.