Vat dyes, dyeing with ; regenerated celluloses, dyeing ; printing.--The fastness and vividness of the dyeings or printings on vegetable or regenerated cellulose fibres obtainable by the use of salts of sulphuric acid esters of leuco vat dyestuffs are improved by impregnating the fibres, prior to the application of the said ester salts, with such organic bases or salts thereof as are capable of forming insoluble or diffucultly soluble salts with the esters. Suitable organic bases and salts thereof are, for example, condensation products of chlorinated paraffins with ammonia or polyethylene-polyamines, cyclohexylmethyldiethylammonium iodide, dimethyltetrahydroquinaldinium iodide, the tetramethylammonium methyl sulphate of mono-oleylethylenediamine or of monostearyl-p-phenylenediamine, mixtures of higher polyethylene-polyamines, octodecylpyridinium bromide, triphenylbenzylphosphonium chloride and triphenyl-3 : 4-dichlorobenzylphosphonium chloride. The following examples are specified : (1) Raw or bleached cotton yarn is treated with an aqueous solution at 35 DEG C. containing the condensation product of trichlorinated paraffin with a mixture of polyethylene-polyamines, squeezed, dried and dyed by treatment for \ba1/2\be hour in a bath at 40--30 DEG C. containing the sodium salt of the sulphuric acid ester of leuco 6 : 6<1>-diethoxy-2 : 2<1>- bisthionaphtheneindigo, sodium nitrite and sodium sulphate, squeezing, immediately developing in dilute sulphuric acid at 75 DEG C., rinsing, neutralizing and soaping at the boil ; the vat dyestuff ester salt may be replaced by the corresponding ester salts of Bz-2 : Bz-2<1>-dimethoxydibenzanthrone, 5<1> : 7<1>-dibromo-2<1>-indole-2-anthraceneindigo, benzoquinone-di-p-chloranilide, 4-methyl-6-chloro-6<1>-methoxythioindigo, the dyestuff of the example of Specification 289,154, 2 : 1-naphthothioindigo, 4 : 4<1>-dimethyl - 6 : 6<1> - dichloro - bis - thionaphtheneindigo or 7 : 7<1>-dimethyl-5 : 4<1> : 6-trichlorothioindigo; the impregnation with the organic base may be effected in a bath made weakly acid, e.g. with acetic acid and deeper shades may be obtained by applying a larger amount of the base by salting out; (2) Cotton yarn or fabric is impregnated for \ba1/2\be hour with an aqueous solution at 35 DEG C. containing triphenyl-3 : 4-di chlorobenzylphosphonium chloride and dyed as in (1) with an alkali salt of the sulphuric acid ester of the leuco compound of 4 : 4<1>-dimethyl-6 : 6<1>-dichloro-bis-thionaphtheneindigo, the dyestuff of the example of Specification 289,154, [Class 2 (iii)], or benzoquinone-di-p-chloranilide, or cotton yarn or fabric is impregnated for \ba1/2\be hour with an aqueous solution at 35 DEG C. containing condensation product of (1) and the above phosphonium compound and printed with an alkali salt of the sulphuric acid ester of the leuco compound of benzoquinone-di-p-chloranilide, 6 : 6<1>-diethoxy-2 : 2<1>-bis-thionaphtheneindigo, 2 : 1-naphthothioindigo or 4-methyl-6-chloro-6<1>-methoxythioindigo; (3) Cotton yarn or fabric is treated for \ba1/2\be hour with an aqueous solution at 35 DEG C. of octodecylpyridinium bromide, a condensation product of halogenated paraffin with ammonia, cyclohexylmethyldiethylammonium iodide, dimethyltetrahydroquinaldinium iodide, a mixture of higher polyethylenepolyamines, triphenylbenzylphosphonium chloride, the trimethylammonium methyl sulphate of monooleylethylenediamine or of mono-stearyl-p-phenylenediamine, and dyed with an alkali salt of the sulphuric acid ester from the leuco compound of 6 : 6<1>-diethoxy-2 : 2<1>-bis-thionaphtheneindigo or 4-methyl-6-chloro-6<1>-methoxythioindigo; (4) Yarn or fabric of viscose or other regenerated cellulose is treated for \ba1/2\be hour with a neutral, acid or alkaline aqueous solution at 35 DEG C. of bases obtainable by reaction of trichlorinated paraffin with polyethylenepolyamines, and/or of triphenyl-3 : 4-dichlorobenzylphosphonium chloride and dyed with an alkali salt of the sulphuric acid ester of the leuco compound of benzoquinone-di-p-chloranilide, 4-methyl-6-chloro-6<1>-methoxythioinidgo or 6 : 6<1>-diethoxy-2 : 2<1>-bis-thionaphtheneindigo. Cyclohexylmethyldiethylammonium iodide is obtained by interaction of cyclohexyldiethylamine with methyl iodide. Dimethyltetrahydroquinaldinium iodide is obtained by exhaustive methylation of tetrahydroquinaldine with excess of methyl iodide. Triphenylbenzylphosphonium and triphenyl-3 : 4-dichlorobenzylphosphonium chlorides are obtained by interaction of triphenylphosphine with benzyl and 3 : 4-dichlorobenzyl chlorides respectively.