The photocatalysed decolorization of two selected dye derivative neutral red (1) and toluidine blue (2) has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions. The decolorization was studied by monitoring the change in concentration of organic dyestuff employing UV spectroscopic analysis technique as a function of irradiation time. The decolorization was investigated using various parameters such as, different types of TiO2, reaction pH, catalyst concentration, concentration of organic dyestuffs, and in the presence of electron acceptors like hydrogen peroxide (H2O2) and potassium bromate (KBrO3) besides molecular oxygen with an aim to determine the optimal decolorization condition for the decomposition of compounds under investigation. (c) 2007 Published by Elsevier B.V.