Decolourisation and mineralization of an indigoid dye, C.I. Acid Blue 74, was conducted using Fe-ZSM5 zeolite as a catalyst in the presence of UV-C light and H2O2. The effects of different parameters such as amounts of catalyst, initial concentration of the dye and H2O2 and initial pH of the dye solution on the degradation efficiency of the process were assessed. The results indicated that by using 21.4 mmol l(-1) of H2O2 and 0.5 g l(-1) of the catalyst at pH 5, about 57% total organic carbon of a solution containing 8.56 x 10(-5) mol l(-1) Acid Blue 74 could be removed after 120 min in a 2 l batch photo-reactor. Leaching tests indicated that the activity of the catalyst is not due to leached iron ions, although an amount of about 0.3 mg l(-1) iron ions was found in the aqueous solution. Significantly lower concentration of Fe2+ and Fe3+ in the solution after the treatment could give a great advantage to UV/Fe-ZSM5/H2O2 system over the homogeneous Fenton-type system. It was found that by using this catalyst, it is possible to expand the range of pH values for which Fenton-type oxidation can occur and no iron hydroxide sludge is formed. It was also observed that catalytic behaviour could be reproduced in consecutive experiments without a considerable drop in the process efficiency. (c) 2008 Elsevier B.V. All rights reserved.