Polyaniline (PA) and sulfonated PA samples were prepared and subjected to thermogravimetric analysis (TGA) in both vacuum and inert atmospheres. The gas phase degradation products were analyzed with gas chromatography (GC). The thermal degradation of polyaniline base was found to follow apparent second-order reaction kinetics with an activation energy of 30 kcal/mol. Two major weight loss regimes were observed in the TGA curve of sulfonated polyaniline. The first regime showed apparent fourth-order reaction kinetics with an activation energy of 47 kcal/mol; the second showed an apparent third-order reaction with an activation energy of 32 kcal/mol. The degradation products from PA and sulfonated PA were compared to those predicted by a previously proposed degradation mechanism for polyaniline hydrochloride. The absence of key degradation products indicates that sulfonated PA does not have the same degradation mechanism as polyaniline hydrochloride.