The aim of this work was to investigate radiolytic decomposition of selected widely used compounds from different classes of pesticides, including imidazole fungicides (carbendazim) and organophosphorous pesticides (chlorfenvinphos). Using HPLC with UV/Vis and fluorometric detection, ion-chromatography and LC/MS methods, the effectiveness of decomposition was examined in different irradiation conditions, together with the identification of the products of decomposition. Monitoring of toxicity changes as a result of irradiation was carried out using Microtox bioluminescence test and Daphtoxkit test.