Reactive disperse mono-azo dyes containing a β-hydroxy-ethyl sulfonyl sulfuric ester group in diazo component have been synthesized. The preparation of anthraquinone derivatives with the same reactive group are also studied. These dyes reacted chemically in weak alkali medium with synthetic polyamide fibres

such as nylon 66 and 6. The dyeing properties of both azo- and anthraquinone reactive disperse dyes on nylon 66 and 6 are being studied. The fastness properties of the dyed substrate are also examined. As expected

these dyes showed bright colours on various substrates

and the dyed fabrics have good fastness to light and wet treatment. The formation of the covalent bond between the reactive group and nylon fibre is proved and discussed. The reactive disperse dyes containing β-hydroxy-ethyl-sulfonyl-sul-furic ester group behaves the important characterictics of either acid reactive or disperse dyes for dyeing polyamide fibres. These dyes are suitable for dyeing various kinds of polyamide fibres as well as natural silk

tussah silk and crepe fabrics of silk with cellulose acetate and others.