The photocatalytic degradation of an insecticide derivative, acetamiprid has been investigated in aqueous suspensions of titanium dioxide (TiO2) as a function of irradiation time under a variety of conditions using UV-Vis and HPLC analysis techniques. The degradation kinetics were studied under different conditions such as types of TiO2, catalyst and substrate concentration, reaction pH and in the presence of electron acceptors like hydrogen peroxide (H2O2), potassium bromate (KBrO3), and potassium persulphate (K2S2O8) besides molecular oxygen (O-2). The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst, Degussa P25 was found to be more efficient as compared to other TiO2 powders used under these studies. The model compound was found to degrade more efficiently in alkaline pH and all electron acceptors enhanced the degradation rate. GC/MS analysis of the irradiated samples indicated the formation of several by-products. A probable mechanism for the formation of by-products has been proposed. (C) 2010 Elsevier B.V. All rights reserved.