The photocatalytic degradation of an antibiotic norfloxacin [1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(l-piperazinyl)-3-quinoline-carbox ylic acid, 1], has been investigated in aqueous suspensions of titanium dioxide (TiO2) under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation kinetics were investigated under different conditions such as different types of TiO2, pH (ranging from 4 to 11), catalyst concentration (0.5-3 g L-1), substrate concentration (0. 15-0.5 mM) and in the presence of electron acceptor such as hydrogen peroxide (H2O2, 10 mM) besides molecular oxygen. Semiconductor titanium dioxide (Degussa P25) was found to be more efficient as compared with other photocatalysts. (c) 2006 Elsevier B.V. All rights reserved.