The photocatalytic degradation of four reactive dyes using TiO2 was investigated in suspended and immobilized systems under solar irradiation. Batch degradation experiments were carried out at initial concentrations ranging from 25 to 100 mg l(-1) and at a catalyst loading of 0.5-1 g l(-1). The studies on batch photocatalytic degradation of four dyes, showed about 30-70% colour removal depending on the initial dye concentration, dye structure (functional group and reactivity of dyes) and the amount of catalyst. The thin film immobilized surface photoreactor was able to give nearly 90-98% colour removal depending on the initial concentration and exposure time. Flow rate has noticeable effect on colour removal particularly at higher concentration (100 mg l(-1)). High colour removals obtained with solar radiation indicated effectiveness of this process and its potential for practical application. (c) 2006 Published by Elsevier Ltd.