The thermal degradation and kinetics of poly(2,6-dimethylphenylene oxide) (PPO) were studied by high-resolution thermogravimetry. The thermogravimetry measurements were conducted at an initial heating rate of 50 degrees C min(-1), resolution 4.0, and sensitivity 1.0 in both nitrogen and air from room temperature to 900 degrees C. A two-step degradation process was clearly revealed in air at the temperatures of 430 degrees C and 521 degrees C. The thermal degradation temperatures and kinetic parameters of the PPO appear to be higher in air than in nitrogen, indicative of a higher thermostability in air. The temperature, activation energy, order, and frequency factor of the thermal degradation of the PPO in nitrogen are 419 degrees C, 100-120 kJ mol(-1), 0.5, and 13-17 min(-1), respectively.