Photocatalytic degradation of methylene blue (MB) in TiO2 aqueous suspensions using microwave (MW) powered electrodeless discharge lamps (EDLs) was studied. MB of initial concentration 100 mg/l was mainly decomposed in the process of photocatalytic degradation using EDLs (PCD/EDLs) after 15 min of irradiation. The corresponding mineralization efficiency was 45%. The influence of factors as EDLs, solution volume and TiO2 catalyst dosage on the decomposition of MB in the PCD/EDLs process was also investigated. The optimal decomposition efficiency was observed when EDLs-4 (four 10 rum x 50 rum EDLs), solution volume of 50 ml and TiO2 catalyst dosage of 1-4 g/l were used in the study. The PCD/EDLs process was promising in treating MB polluted water. (c) 2005 Elsevier B.V. All rights reserved.