The photocatalytic degradation of an anthraquinone dye Vat Yellow 4 in aqueous solution with TiO 2 -P25 (Degussa) as photocatalyst has been investigated under solar and UV irradiation. The study on the effect of various photocatalysts reveals that TiO 2 is the best catalyst in comparison to other commercial photocatalysts. The effect of operational parameters such as catalyst loading and initial dye concentration on the decolourisation and degradation under UV irradiation in TiO 2 suspension has been investigated to find out the optimum conditions. The decolourisation and degradation kinetics was found to follow first-order kinetics. A study on the effect of electron acceptors reveals that both decolourisation and degradation increase in the presence of the electron acceptors such as H 2 O 2 , (NH 4 ) 2 S 2 O 8 and KBrO 3 up to an optimum dosage beyond which the enhancement effect is negligible. The presence of inorganic additives was found to decrease the degradation.