Azo dyes; azo dyes, forming on the material; regenerated celluloses, dyeing.--Trisazo dyes are obtained by coupling a diazotized amine of the benzene or naphthalene series with a 1-(m- or p-amino)-aryl-3-methyl (or 3-carboxy)-5-pyrazolone, diazotizing the resulting aminoazo compound, coupling with a usual middle component, again diazotizing and coupling in acid, neutral or alkaline medium with a naphthol, naphthylamine or aminonaphthol or a sulphonic acid of these or a naphtholcarboxylic acid or an N-substituted naphthylamine or aminonaphthol sulphonic acid, the end component being other than a 1 : 8-aminonaphtholsulphonic acid or an N-acyl derivative thereof when the third component is a 1-amino-2-naphthol ether or a derivative thereof. When the N-substituent contains a diazotizable amino group the trisazo product may be diazotized and coupled with a component in substance or on the fibre. In examples the preparation is described of the following dyestuffs: (1) sulphanilic acid --> 1-(m-amino)-phenyl-3-methyl-5-pyrazolone --> 2 : 5-dimethoxyaniline --> (in ammonia solution) 1-p-(amino) benzoylamino-8-naphthol-4-sulphonic acid, which dyes cotton clear blueish green and may be diazotized and developed on the fibre with 1-phenyl-3-methyl-5-pyrazolone to give clear yellowish green shades, (2) sulphanilic acid --> 1-(m-amino)-phenyl-3-methyl-5-pyrazolone --> 1-amino-2-ethoxynaphthalene-6-sulphonic acid --> 2-naphthol-3 : 6-disulphonic acid, which dyes cotton and viscose artificial silk blueish green, (3) 2-naphthylamine-4 : 8-disulphonic acid --> 1-(m-amino)-phenyl-3-methyl-5-pyrazolone --> 1-naphthylamine-2-thioglycollic acid --> (in ammonia solution) 2 - (p - amino) - benzoylamino - 5 -naphthol - 7-sulphonic acid, which dyes cotton blueish green and may be diazotized and developed on the fibre with acetoacetic o-chloranilide to give clear yellowish green shades fast to washing, (4) the aminodisazo dyestuff in (3) --> (in pyridine solution) 2-methylaminonaphthalene-7-sulphonic acid, which dyes cotton and viscose artificial silk blue-green, (5)2 : 5-dichloraniline-4 - sulphonic acid --> 1-(m-amino) phenyl - 3 methyl - 5 - pyrazolone --> 1 - amino - 2-ethoxynaphthalene - 6 - sulphonic acid --> (in ammoniacal pyridine solution) 2-phenylamino-5-naphthol-7-sulphonic acid, which dyes cotton greenish blue, (6) 2-naphthylamine-8-sulphonic acid --> 1 - (p-amino) phenyl - 3 - methyl - 5 - pyrazolone --> 1-naphthylamine- 7 -sulphonic acid --> (in ammoniacal pyridine solution) 1-(o-chloro) benzoylamino-8-naphthol-3 : 6-disulphonic acid, which dyes cotton yellowish green, (7) m-aminobenzoic acid --> 1-(p-amino)phenyl-5-pyrazolone-3-carboxylic acid --> 1-naphthylamine --> (in ammonia solution) 1-amino-8-naphthol-2 : 4-disulphonic acid, which dyes cotton green, (8) sulphanilic acid --> 1-(p-aminosulphophenyl-3-methyl-5-pyrazolone --> 2 : 5-dimethoxyaniline --> (in ammoniacal pyridine solution) 1-acetylamino-8-naphthol-3 : 6-disulphonic acid, which dyes cotton clear green, (9) metanilic acid --> 1-(4<1>-amino-1<1>-naphthyl)-3-methyl-5-pyrazolone --> 1-amino-2-ethoxy-naphthalene-6-sulphonic acid --> (in ammoniacal pyridine solution) 2 - phenylamino-5-naphthol-7-sulphonic acid, which dyes cotton blue-green, (10) metanilic acid --> 1-(m-amino)-phenyl-3-methyl-5-pyrazolone --> 1-amino-2-ethoxynaphthalene-6-sulphonic acid --> (in ammoniacal pyridine solution) 1 : 5-amino-naphthol, which dyes cotton blue-green, (11) sulphanilic acid --> 1- (p-amino) phenyl-3-methyl-5-pyrazolone --> 1-naphthylamine-2-thioglycollic acid --> 1-naphthol, which dyes cotton blue-green, (12) the aminodisazo dyestuff in (3) --> 2 : 3-oxynaphthoic acid, which dyes cotton blue-green. 1 - (p-Aminosulpho) phenyl-3-methyl - 5 - pyrazolone is obtained by sulphonating 1-(p-amino)-phenyl - 3 - methyl - 5 - pyrazolone with chlorosulphonic acid in tetrachlorethane; the sulpho group is probably in the 3<1>-position. 1 -(4<1>-Amion-1<1>-naphthyl- 3 - methyl - 5 - pyra-zolone is obtained by reducing diazotized 4-nitro-1-naphthylamine to the nitrohydrazine, condensing the product with acetoacetic ester and reducing the nitro group.