This paper studies water soluble disperse dyes containing carboxy-methyl-sulfonyl group (-SO2CH2COOH). Monoazo dyes with the carboxy-methyl-sul-fonyl group in diazo component and the anthraquinone derivatives of the same group have been synthesized. The azo dye(I) was prepared as follows: The other azo dyes were similarly prepared. The anthraquinone dyes were prepared as follows- Ammonium salts of this type of dyes are water soluble. These dyes are suitable for pad dyeing or printing on polyester fiber and polyester/cotton blends in either weak acid

neutral or weak alkali medium without a dispersing agent. The solubilizing carboxyl group is believed to be decarboxylized at thermal fixation temperatures during dyeing. The formation of methyl sulfonyl group(-SO2CH3)from carboxy-methyl-sulfonyl group after fixing on the fiber was proved by thin-layer chromatography and infrared spectra. Their fastness properties are good and the fastness to sublimation is -excellent.