Abstract: Dyestuffs of the general formula: ##STR1## IN WHICH THE RADICAL --CH=--CN is fixed in the 4- or 5-position, X represents a hydrogen or chlorine atom, the benzene nucleus A is unsubstituted or substituted by at least one chlorine atom or alkyl, alkoxy or acylamino group, m is the number 0 or 1, and B represents the residue of a coupling compound containing no sulphonic or carboxylic acid group.The dyestuffs in which m represents zero may be prepared by diazotizing a base of the formula: ##STR2## and coupling the diazo derivative with a coupling compound BH wherein X and B have the same significance as set out above.The dyestuffs in which m is equal to 1 may be prepared by coupling the diazo derivative of a base of the formula: ##STR3## with an amine of the formula: ##STR4## diazotizing the amino-monoazo dyestuff thus obtained and coupling with a coupling compound BH wherein ##STR5## have the same significance as set out above. The dyestuffs may be used for the coloration of synthetic fibres.