In this paper, photocatalytic degradation studies of a hazardous water soluble xanthene dye cyanosine in aqueous suspensions of titanium dioxide under a variety of conditions, viz., catalyst concentration, substrate concentration, pH, temperature and electron acceptor hydrogen peroxide (H2O2) have been reported. It was observed that photocatalytic degradation by TiO2 is an effective, econormc and faster mode of removing cyanosine from aqueous solution. The optimum conditions for the degradation of the dye was dye concentration 1 x 10(-4) M, pH 8, catalyst concentration 0.04 g/L and temperature +/- 30 degrees C. Chemical oxygen demand and dye absorbance of the photodegraded dye solution substantially decreased. (c) 2007 Elsevier B.V. All rights reserved.