Compounds which contain ammonium groups and sulphonic acid groups and which, in the betaine form, correspond to the formula ##STR1## wherein X denotes --CO-- or --SO.sub.2 --,R.sub.1 denotes hydrogen or alkyl,R.sub.2, R.sub.3 and R.sub.4, independently of one another denote alkyl, alkenyl or aralkyl, orR.sub.4 denotes ##STR2## Y denotes alkylene or xylylene, m denotes 1 or 2,n denotes 0 or 1, andR.sub.5 and R.sub.6, independently of one another, denote hydrogen, alkyl, alkoxy or halogen, and in addition, if n=1,R.sub.2 or R.sub.4 denotes amino, alkylamino, dialkylamino, aryl or cycloalkyl,R.sub.2 and R.sub.3, together with the nitrogen atom which is bonded to them, denote a 5-membered or 6-membered ring,R.sub.2, R.sub.3 and R.sub.4, together with the nitrogen atom which is bonded to them, denote a pyridinium ring, a group of the formula ##STR3## or hydrogen, Y denotes arylene, benzylene or a radical of the formula ##STR4## Z denotes a direct bond, --(CH.sub.2).sub.p --, --O--, --O--(CH.sub.2).sub.p --O--, --SO.sub.2 --, --NHCO--, --NHCONH--, --NHCO--(CH.sub.2).sub.p --CONH-- or --CONH--(CH.sub.2).sub.p --NHCO--,p denotes 1, 2 or 3, andR.sub.7 denotes hydrogen, alkyl, alkoxy or halogen, and wherein the cyclic and acyclic radicals can contain non-ionic substituents, their preparation and their use as coupling components in the preparation of azo dyestuffs.