Azo dyestuffs of the general formula <FORM:0589280/IV/1> wherein R1 and R2 represent aromatic residues of the benzene series, of which one contains a hydroxy group in o-position to the azo linkage, but which, apart from this, are free from aromatically bound hydroxy, carboxyl or sulphonic groups, and in which R2 carries the substituted amino group and the azo linkage in p-position to one another, x represents hydrogen or an alkyl residue which contains not more than 4 carbon atoms directly connected to one another, and which may contain substituents, e.g. a halogen atom or an alkoxy, hydroxy or carboxyl group, and y represents an acyl residue containing a carboxyl group and at least one double bond (which may be present in an aromatic ring), are manufactured by the action of one molecular proportion of a poly-basic carboxylic acid containing at least one double bond, or a reactive derivative thereof, on one molecular proportion of an aminoazo dyestuff of the general formula <FORM:0589280/IV/2> (obtainable by coupling a diazotized o-aminophenol, or an ester thereof with an aromatic sulphonic acid, e.g. benzene- or p-toluenesulphonic acid, with a primary or secondary amine of the benzene series capable of coupling in p-position to the amino group, and, if necessary, removing the sulphonic acid residue by saponification). The acids are preferably employed in the form of their halides, e.g. chlorides, esters with alcohols of low boiling point, or anhydrides, and the reaction may be carried out in the presence of solvents such as benzene, toluene, chlorobenzene, solvent naphtha or alcohols, e.g. methyl or ethyl alcohol, and (when an acid is split off) advantageously with the addition of an acid-binding agent, e.g. sodium acetate or carbonate, calcium hydroxide or carbonate or magnesium oxide, or by the use of a solvent having basic properties, e.g. dimethylaniline or pyridine. When the hydroxy group is attached to R1, the dyestuffs may also be made by diazotizing a primary amine of the general formula <FORM:0589280/IV/3> and coupling with a monohydric phenol capable of coupling in o-position to the hydroxy group. The products, especially in the form of their alkali metal or ammonium salts, are soluble in water and may be used for dyeing or printing animal fibres (e.g. wool and silk) and especially artificial materials of acetylcellulose (e.g. cellulose acetate artificial silk) or of superpolyamides or superpolyurethanes, giving mainly yellow to red shades. In example: (1) the p-toluenesulphonic ester of o-aminophenol is diazotized and coupled with the sodium salt of o-anisidine-o -methanesulphonic acid, and the product is saponified with aqueous alcoholic caustic soda solution, heated with phthalic anhydride in chlorobenzene and neutralized with alkali, e.g. ammonia; the phthalic anhydride may be replaced by maleic anhydride; (2) an aminoazo dyestuff prepared as in (1) except that the coupling component is o-toluidine-o -methanesulphonic acid, is heated with maleic anhydride in ethyl acetate and the product is neutralized with ammonia; the maleic anhydride may be replaced by phthalic anhydride, the ethyl acetate by benzene, toluene or solvent naphtha, and the aminoazo dyestuff by, for example, the dyestuffs o-anisidine or p-chloraniline --> m-aminophenol; (3) cellulose acetate artificial silk is dyed yellow with the first dyestuff of (1) from a bath containing sodium sulphate; (4) textile goods are printed with a paste containing the first dyestuff of (1), water, a gum thickening and glycerol and then dried, steamed, rinsed and dried. A number of additional dyestuffs are represented by their formul , and the following further starting materials are specified: for the preparation of the aminoazo dyestuffs <FORM:0589280/IV/4> : as diazo components: 4-, 5- or 6-methyl-, -chloro- or -nitro-2-aminophenol, 4-methoxy-2-aminophenol, 4-methyl-6-nitro - 2 - aminophenol, 4 - nitro - 6 - chloro - 2 - aminophenol, 4 : 6 - dinitro - 2 - aminophenol, 2 - aminophenol-4-sulphonamide, -4-sulphonethylamide and -4-b -hydroxyethyl sulphone; as coupling components: aniline, N -methyl- and N - ethyl - aniline, m - toluidine, N - methyl - m-toluidine, m-anisidine, o-phenetidine, N-methyl-and N-ethyl-o-anisidine, 2-methoxy-5-methylaniline, 2 : 5-dimethoxyaniline, 2 : 5-dimethyl-N - butylaniline, 3 - chloro - N - propylaniline and monoacetyl-m-phenylenediamine; as polybasic carboxylic acids: fumaric acid, chlorophthalic acids, isophthalic acid and naphthalic acid; for the alternative process: as diazo components <FORM:0589280/IV/5> : the monoamides from equimolecular proportions of maleic or phthalic acid and 1 : 4-phenylenediamine or its 3-methoxy-derivative; as coupling components: p-cresol, 3 : 4-dimethylphenol and 3- (or 4-) chloro-4- (or 3-) methylphenol, and also compounds such as m-aminophenol (which must be coupled in such a way as to form an o-hydroxyazo dyestuff and of which the amino group may, if desired, be acylated after coupling). Specifications 11228/95, [Class 15], 298,098, [Class 2 (iii)], and 343,006 are referred to. The Specification as open to inspection under Sect. 91 comprises also the manufacture of dyestuffs of the general formula above in which y represents a saturated acyl residue containing a carboxyl group, or any acyl residue containing a sulpho group. Additional polybasic acids specified for use in the first of the alternative methods above are oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, sulphoacetic, sulphochloracetic, sulphosuccinic, sulphophthalic, sulphonaphthalic and sulphosalicylic acids, and additional dyestuffs are formulated. Reference is also made to the use, as diazo components in the second of the alternative methods above, of derivatives of m-phenylenediamine in which one amino group is acylated with the residue of a polybasic organic acid. This subject-matter does not appear in the Specification as accepted.