In this study, ethylene-propylene-diene terpolymer residues (EPDM-r) from the automotive industry were analyzed by thermogravimetric analysis (TGA) for determination of the activation energy (E(a)) of decomposition by the Flynn-Wall-Ozawa (FWO) method. The degradation mechanism was determined by the method of Criado et al. Analysis of the nonvulcanized EPDM gum (EPDM-g) and paraffinic oil used in the composition of the compound was also carried out. The E(a) values for the decomposition of the EPDM-g and paraffinic oil remained constant with the conversion, but for the EPDM-r decomposition, they changed due to the initial oil elimination followed by decomposition of the EPDM fraction. It was observed that removal of the paraffinic oil occurred less easily in the tridimensional vulcanized network, and there were differences in the elimination mechanism. The EPDM degradation mechanism was also affected by vulcanization and the fillers present in the compound. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 1053-1057, 2011