Titanium dioxide mediated photocatalysed degradation of a textile dye derivative, acid orange 8 (1), was investigated in aqueous suspensions of titanium dioxide by monitoring the depletion of total organic carbon (TOC) content as a function of irradiation time under a variety of conditions. The degradation kinetics were studied under different conditions such as pH, catalyst concentration, substrate concentration, different types of TiO2 and in the presence of electron acceptors such as hydrogen peroxide (H2O2) and potassium bromate (KBrO3) besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient compared with other photocatalysts. The dye was found to be adsorbed on the surface of the photocatalyst at acidic pH.