The thermal stability of blends obtained from the mixture of 4-dodecylbenzenesulfonic acid doped polyaniline (PANI(DBSA)) and a terpolymer of ethylene-propylene-5-ethylidene-2-norbornene (EPDM) by casting from organic solvents, was studied by thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) under nitrogen atmosphere. For the PANI(DBSA) complex and PANI(DBSA)/EPDM blends the TGA results showed more than one stage of degradation, of which the second (temperature range 380–520 °C) was observed to be the most significant. Apparently, in this stage, the simultaneous degradation of the bound dopant, the PANI and the elastomer occurred. The activation energy ( E) for the crosslinked blends was in the range 180–250 kJ mol −1, higher values than those determined for pure components and non crosslinked blends which were in the range 150–210 kJ mol −1. The E values also indicated that the effects due to the PANI(DBSA) content and maleated EPDM were not significant and that the mechanism of degradation of both systems studied was associated with a random scission of the chain. The FTIR spectra for the PANI(DBSA)/EPDM crosslinked blend showed typical absorption bands associated with saturated and unsaturated hydrocarbons, water, carbon dioxide and nitrogen containing compounds.