Thermogravimetric analysis, carried out in a pure oxygen flow both in isothermal and constant-rate heating conditions, is proposed as an analytical technique for the estimation of thermal endurance parameters (the temperature index and halving interval) of polymeric materials, according to the short-term procedure suggested by the IEC 61026 Standard. This technique was applied for the determination of the activation energy of the degradation process of three thermoplastic polyesters used in the electrical and packaging industries: poly(ethylene terephthalate), poly-(buthylene terephtalate), and poly(ethylene naphthalate). The results obtained are presented and compared with results previously derived by the long-term conventional procedure described in IEC 60216; satisfactory agreement of the thermal endurance parameters was generally observed. (c) 2005 Wiley Periodicals, Inc.