Diethyl maleate, maleic anhydride and dicumyl peroxide in different ratios were directly added to molten polymeric mixtures based on ethylene-co-propyl e ne (EPM) and polyamide 6 (PA6) to perform in one-step the functional groups grafting and branched copolymer formation necessary to obtain compatibilized products. The characterization of the blends by selective solvent extraction and IR and NMR analysis of the various fractions allowed to evidence the occurrence of maleate grafting on both EPM and PA6 as well as the formation of raft copolymers at the interface. The effect of the reactions on phase morphology development and thermal properties was evaluated by SEM and DSC analysis respectively in order to investigate the compatibilization extent in comparison with the conventional two-steps procedure. Besides tests about mechanical properties of samples produced by the extrusion were carried out. (c) 2005 Elsevier Ltd. All rights reserved.