The removal of the herbicide simazine (2-chloro-4,6-bis(ethylamino)-s-triazine) in aqueous phase has been carried out continuously by means of Fenton's reagent (Fe(II) +H2O2). The influence of the main operating parameters, Fe(II) concentration (5.0 x 10(-5) to 4.0 x 10(-4) M), pH (2-6) and temperature (10-30 degreesC) has been studied. Based on HPLC analysis, the main route of simazine removal has been proposed to be the dechlorination reaction to generate 2-hydroxy-4,6-bis(ethylamino)-s-triazine. Nevertheless the dealkylated first intermediate of the herbicide was also identified by chromatography techniques. By means of a pseudoempirical model based on the classic Fenton's chemistry and the mass balances for a continuos perfectly mixed reactor, the theoretical evolution profiles of the species involved in the process have been calculated. (C) 2003 Elsevier B.V. All rights reserved.