An azo dyestuff of the formula STR1 in which D is benzene or naphthalene, optionally substituted by sulfonic acid, carboxy, hydroxy, halogen, nitro, amino, lower alkylamino, lower alkyl, lower alkoxy, lower alkylsulfonyl, trifluoromethyl, cyano, cyclohexyloxycarbonyl, sulfonic acid-N-lower alkylamide, sulfonic acid N-lower alkoxy-loweralkylamide, lower acylamino, phenylazo, sulfophenylazo, sulfonaphthylazo, β-sulfatoethylsulfonyl, β-sulfatoethylsulfonamido, aminosulfonyloxy and a fibre-reactive radical bound via an amino group; or is thiazole, quinoline, benzthiazole, 6-methylbenzthiazole, 1,3,5-thiadiazole or benzisothiazole; R is hydrogen, lower alkyl, lower halogenalkyl, lower hydroxyalkyl, lower acylamino-lower alkyl, phenyl-lower alkyl, phenyl, halogenphenyl, lower alkoxyphenyl, lower acylaminophenyl, lower acylamino-lower alkyl and amino-lower alkyl, in which the amino group is optionally substituted by a fibre-reactive radical; R' is hydrogen, lower alkyl, phenyl-lower alkyl, phenyl, halogenphenyl and lower alkoxy-phenyl; and V is hydrogen, lower alkyl and phenyl, optionally substituted by halogen, nitro, cyano, amino, lower acylamino and a fibre-reactive radical bound via an amino group; and the heavy metal complex compound thereof, is suitable for dyeing and printing widely different types of materials, such as natural and synthetic polyamide and cellulose materials of fibrous structure. These dyestuffs show an excellent building-up capacity and valuable yellow pure and brilliant shades. The dyeings and prints exhibit a good stability to acids and alkalis, a good fastness to light and a good fastness to wet processing.