We report here the investigations on the thermal and thermo-oxidative degradation kinetics of a technologically important conducting polymer poly(3-hexyl thiophene) (P3HT) as measured in nitrogen and air medium, respectively. The derivative thermogravimetric results clearly indicate single stage decomposition for thermal degradation while triple stage decomposition is observed for thermo-oxidative degradation. The Vyazovkin model-free kinetics method was applied to calculate the effective activation energy (E-alpha) of the degradation process as a function of conversion. The E-alpha values are higher in nitrogen than in air medium. In nitrogen medium, the E-alpha value remains almost constant up to an extent of conversion. alpha = 90%. Interestingly, in air medium, the E-alpha shows an initial minimum, then increase and exhibits a maximum at alpha = 45%. decreases steadily and plateaus thereafter. This reveals that the degradation mechanism of P3HT in air medium is complex. The model-free isothermal predictions could be of use in correlating the service temperature of this conducting polymer. (C) 2009 Elsevier B.V. All rights reserved.