Insoluble azo dyestuffs are produced in substance or on the fibre by combining a diazo, tetrazo, or diazoazo compound, not containing a sulphonic or carboxylic group, with monoacylacetyl derivatives of amines of the general formula NH2-R-X-R1 where R = aryl, R1 = the same or different aryl or a heterocyclic or acyclic residue of a compound containing a methylene group capable of coupling, and X = an azo-or azoxy-group or the residue of a five-membered heteroatomic nucleus. The monoacylacetylamino compounds are made by heating, advantageously in a solvent or diluent, acetoacetic ester or a homologue or analogue such as benzoylacetic ester, with amines of the above formula: such amines include the following:-amino-azoxy compounds; aminoazo compounds obtainable by coupling diazo compounds with middle components; aminoazo compounds obtainable by coupling nitro- or acylamino-diazo compounds with phenols or bodies containing an active methylene group such as methylphenylpyrazolones or derivatives of b -ketonealdehydes, for example acetoacetic acid derivatives or acetylacetone, and reducing or saponifying; amino-substituted phenylpseudo-azimino-benzenes, phenyl-benziminazoles, and phenyl-benzothiazoles. As diazo components may be used aniline and its homologues and substitution products, naphthylamine, aminoanthraquinones, aminoazo compounds, and diamines such as dianisidine, dichlorbenzidine, diaminodiphenylether, diamino-azo- and diaminoazoxy compounds. The dyestuffs are suitable for production of lakes and pigments and are of various shades of yellow. Examples are given in which yellow lake-dyestuffs are produced from o-chloraniline and acetoacetyl-4-amino-41-chlor-azobenzene, and from 2 : 5-dichloraniline and acetoacetyl-dehydrothiotoluidine. The tints of a large number of dye-stuffs are tabulated, the following components being specified: diazo components:-p-toluidine, o-chloraniline, 2 : 5-dichloraniline, 4-, 5-, or 6-chlor-2-toluidine, 4-chlor-3-toluidine, 4-chlor-2-anisidine, 4-chlor-2-nitraniline, 2-chlor-4-nitroaniline, o-nitraniline, 3-nitro-4-toluidine, 5-nitro-2-toluidine, 4-nitro-2-anisidine, 4-nitro-1-naphthylamine, o-amino-diphenylether, a - or b -aminoanthraquinone, o- or m-aminoazotoluene, o-phenetol-azo-a -naphthylamine, dianisidine: coupling components:-acetoacetyl-4-aminoazobenzene, acetoacetyl-4-aminoazoxybenzene, acetoacetyl-4-amino-41-chloro-azobenzene, acetoacetyl-4-amino-31-nitroazobenzene, acetoacetyl - o - aminoazotoluene, acetoacetyl-4-amino-1 - phenylazo - naphthalene, acetoacetyl-41-amino-21-methylphenyl-azo-1-naph thalene, acetoacetyl-41-aminobenzene-azo-3-methyl-1-phenyl-5 -pyrazolone, acetoacetyl-41-aminobenzene-azo-p-cresol, acetoacetyl-dehydrothiotoluidine.ALSO:Fast yellow shades are produced on the fibre by impregnating with certain monoacylacetylamino compounds and dyeing or printing with diazo-, tetrazo-, or diazo-azo-compounds not containing sulphonic or carboxylic groups, or by printing by the nitrosamine process. The mono-acylacetylamino compounds used are those of the monamines of the formula NH2-R-X-R1 where R=aryl, R1=the same or different aryl or a heterocyclic or acyclic residue containing a methylene group capable of coupling, and X=an azo- or azoxy-group or the residue of a five-membered heteroatomic nucleus; they may be derived from acetoacetic ester or a homologue or analogue such as benzoylacetic ester and amines such as the following :-aminoazoxy compounds; aminoazo compounds obtained by coupling diazo compounds with middle components; aminoazo compounds obtained by coupling nitro-diazo-or acidylamino-diazo-compounds with phenols or bodies containing an active methylene group such as methylphenyl-pyrazolones or derivatives of b -ketone-aldehydes such as aceto-acetic acid derivatives or acetylacetone, and reducing or saponifying; amino-substituted phenylpseudo-azimino-benzenes, phenyl-benziminazoles, and phenyl-benzothiazoles. As diazo components may be used aniline and its homologues and substitution products, naphthylamines, aminoanthraquinones, aminoazo compounds, and diamines such as dianisidine, dichlorobenzidine, diaminodiphenylether, diamino azo and diamino azoxy compounds. Examples are given of the production of yellow and reddish yellow shades from the following components :-acetoacetyl-4-aminoazobenzene or acetoacetyl-4-amino-31-nitro-azobenzene and 5 nitro-2-toluidine; acetoacetyl-41-aminobenzene-azo-1-phenyl-3-methyl-5 -pyrazolone or acetoacetyl-41-amino benzene-azop-cresol and 5-chlor-2-toluidine, followed by after-treatment with copper or chromium salts for browner shades, acetoacetyl-dehydrothiotoluidine and o-nitranline. The tints of a large number of dyestuffs are also tabulated.