Azo dyestuffs containing metal in complex union are manufactured by the action of an agent yielding metal, e.g. chromium, copper, iron, aluminium, cobalt, nickel, manganese, zinc, vanadium or titanium, on a disazo-dyestuff constructed according to the scheme R --> R1 \sM R where both R's are diazo-components of which at least one contains a metal complex forming group and R1 is an aryl derivative containing at least two amino-groups and capable of coupling twice. The disazo-dyestuffs may be prepared by coupling two similar or different diazo-compounds, at least one of which contains a metal complex forming group, e.g. those of amines of the benzene or naphthalene series which may contain, in o-position to the diazo-group, hydroxy, carboxyl, alkoxy or the salicylic acid grouping, e.g. those of aniline, naphthylamines, o-aminophenol, o-aminonaphthol, o-aminoalkoxybenzene, o-aminoalkoxynaphthalene, anthranilic acids, o-aminonaphthalenecarboxylic acids, aminosalicylic acids, and the sulpho-, nitro-, alkyl- and halogen-substitution products thereof, with an aryleneamine capable of coupling twice, e.g. a phenylene- or naphthylene-diamine, e.g. 1 : 3-phenylenediamine, its 4-sulphonic acid, 1 : 3-diamino - 4 - methylbenzene, 1 : 3 - naphthylenediamine and their nitro-, alkoxy- and halogen-substitution products. The treatment with an agent yielding metal may be effected in acid, neutral or alkaline medium, with or without a suitable addition such as a salt of an inorganic or organic acid or a free organic acid, in the presence or absence of an organic solvent, e.g. alcohol or pyridine, and in an open vessel or under pressure, and may occur simultaneously with the production of the dyestuff, or in substance, on the fibre or in the dye-bath. One agent yielding metal, or several such agents, simultaneously or successively, may be caused to act on a single dyestuff or mixture of dyestuffs, and one atom or more or less than one atom of metal may be introduced for each metal complex forming group in the dyestuff. Dyestuffs containing less than one atom of metal may be made by causing a metal compound of a dyestuff to act on a dyestuff not containing metal, and the product may be treated further with an agent yielding metal. In a modification of the process, a monoazo-dyestuff R --> R1 containing a metal complex forming group or a mixture of such dyestuffs is treated with an agent yielding metal or mixture of such agents and the product is coupled with a second diazo-compound. The products may be further treated with an agent yielding metal or mixture of such agents especially if the second diazo-compound also contains a metal complex forming group. The complex metal compounds may be used for dyeing animal fibres, e.g. wool or silk, or leather tanned in any manner, e.g. chrome or vegetable tanned. In examples: (1) the dyestuff 4-nitro-2-aminophenol --> 1 : 3-diaminobenzene \sM 4 - nitro - 2 - aminophenol-6-sulphonic acid is prepared and is treated with ferric chloride; the product dyes chrome leather olive-brown tints; (2) the dyestuff 4 - nitro - 2 - aminophenol - 5 - sulphonic acid --> 1 : 3 - diaminobenzene \sM 4 - chloro - 2 - amino - phenol is prepared and treated with ferric chloride and copper sulphate; the product dyes chrome leather reddish-dark-brown tints; (3) the dyestuff 6-nitro-2-aminophenol-4-sulphonic acid --> 1 : 3-diaminobenzene is treated with ferric chloride and the product is coupled with diazotized 4-nitro-2-aminophenol and further treated with ferric chloride; the product dyes chrome leather blackish violet-brown tints; (4) the dyestuff 4-chloro-2-aminophenol --> 1 : 3-diaminobenzene \sM 4 - nitro - 2 - aminophenol - 6 - sulphonic acid is prepared in the presence of ferric hydroxide and nickel hydroxide; the product dyes vegetable and chrome tanned leather dark brown tints; (5) the manganous compound of the dyestuff 4-chloro-2-aminophenol-6-sulphonic acid --> 1 : 3-diaminobenzene is coupled with diazotized 2-aminophenol-4-sulphamide and the product is treated with chromium fluoride; the product dyes chrome leather violet brown tints; (6) the cobalt compound of the dyestuff 4-chloro-2-aminophenol-6-sulphonic acid --> 1 : 3-diaminobenzene is coupled with diazotized 2-aminobenzene-1-carboxylic acid and the product is treated with aluminium acetate; the product dyes leather blackish violet-brown tints; (7) the nickel compound of the dyestuff 4-chloro-2-aminophenol-6-sulphonic acid --> 1 : 3-diaminobenzene is coupled with diazotized 4-acetylamino - 1 - aminobenzene; the product dyes chrome leather reddish-brown tints; (8) the dyestuff 6-nitro-2-aminophenol-4-sulphonic acid --> 1 : 3-diaminobenzene \sM 5-amino-2-oxybenzoic acid is prepared and is treated with ferric chloride; the product dyes leather brown tints; (9) the dyestuff 4-nitro-2-aminophenol --> 1-methyl-2 : 4-diaminobenzene \sM 4 - nitro - 2 - aminophenol - 6 - sulphonic acid is prepared in the presence of ferric hydroxide and copper hydroxide; the product dyes chrome leather dark brown tints; (10) the dyestuff 4 : 6-dinitro-2-aminophenol --> 1 : 3-diaminobenzene-4-sulphonic acid \sM 1-amino-8 - oxynaphthalene - 3 : 6 - disulphonic acid is prepared and is treated with cobaltous sulphate; the product dyes chrome leather dark beige to brown tints; (11) 1 : 3-diaminobenzene is coupled with 6-nitro-1-diazo-2-oxynaphthalene-4-sulphonic acid and then with diazotized 6-nitro-2-aminophenol-4-sulphonic acid and the product is treated with ferric chloride and nickel sulphate; the product dyes leather blackish copper-brown tints; (12) the dyestuff 4 - nitro - 2 - aminophenol --> 1 : 3 - diaminobenzene \sM 4-nitro-2-aminophenol-6-sulphonic acid is prepared in the presence of ferric hydroxide and nickel hydroxide; the product dyes leather olive dark-brown tints; (13) the dyestuff 4-nitro-2-aminophenol-6-sulphonic acid --> 1 : 3-diaminobenzene \sM 4 : 6-dinitro-2-aminophenol is treated with chromium fluoride; the product dyes chrome leather violet brown tints; (14) neutralized chrome leather (box calf, chrome sides, glazed kid, full chrome sheep) is dyed an olive dark-brown tint with the iron-nickel compound of the dyestuff 4 - nitro - 2 - aminophenol --> 1 : 3 - diaminobenzene \sM 4 - nitro - 2 - aminophenol - 6-sulphonic acid; (15) vegetable-tanned sheep, goat or calf leather is similarly dyed. A table gives the shades obtained on chrome leather with further metal - containing dyestuffs, additional diazo-components specified being 4-sulpho-2-aminobenzoic acid and 1 : 5-naphthylaminesulphonic acid.