Five different polyaniline salts have been prepared by chemical polymerization. The thermal stabilities and energies of activation for all the salts under oxygen and nitrogen atmospheres have been determined from thermogravimetric analysis. Polyaniline salts undergo a three step weight loss process in the heating cycle. In the first step, a water molecule escapes from the polymer matrix; in the second step, it is possible that a phase transition occurs, along with evolution of a small percentage (almost-equal-to 2-3%) of adsorbed acid present on the polymer chain; and finally, thermal degradation occurs. It was found that the thermal stability of polyaniline depends on the counter anion used, and the polymer is apparently stable up to 250-degrees-C. The energy of activation for the degradation process has been calculated using five different methods and the results are compared.