The kinetic analysis of the thermogravimetric curves for the thermal decomposition processes of polyaniline in undoped and doped state (udpan and dpan) was performed. Various forms of non-isothermal methods of analysis for determining the kinetic parameters were used. The results show that the apparent activation energies for both udpan and dpan in static air are 126.5 and 78.5 kJ mol(-1), and those in N-2 are 45.2 and 36.6 kJ mol(-1), respectively. The mean reaction orders obtained from integral method for udpan and dpan in static air are 2.1 and 2.0, and those in N-2 are 1.9 and 2.1, respectively. Therefore the reaction function f(alpha) = (1 - alpha)(2) for the thermal decomposition of both udpan and dpan is reasonable. The thermal decomposition processes for udpan and dpan in N-2 may be a random degradation of polymer chain, whereas in air it should be an oxidation degradation involving the participation of oxygen. Thus the maximum of reaction rate in nitrogen is only 20-26% of those in air and the apparent activation energies for them are only 1/2-1/3 of those in air. But the temperatures corresponding to the maximum reaction rate are higher by about 230-320 K than those in air.