The photocatalytic degradation of two selected dye derivatives, Cl Fast Green FCF (1) and Cl Acid Blue 1 (2, Patent blue VF) has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic technique as a function of irradiation time under a variety of conditions. The degradation was studied under different conditions such as different types of TiO2, pH, catalyst concentration, substrate concentration and in the presence of different electron acceptors such as hydrogen peroxide (H2O2), potassium bromate (KBrO3) and ammonium persulphate (NH4)(2)S2O8) besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Hombikat UV 100 was found to be more efficient for the degradation of Fast Green FCF, whereas Degussa P25 was found to be better for the degradation of Patent Blue VF. Dye (2) was found to degrade more efficiently compared to dye (1).