Cellulose, cellulose diacetate (CDA), cellulose triacetate (CTA), cellulose nitrate (CN), and cellulose phosphate (CP) were subjected to dynamic thermogravimetry in nitrogen and air. The thermostability of the cellulose and its esters was estimated, taking into account the values of initial thermal degradation temperature T-d, the temperature at the maximum degradation rate T-dm, and char yield at 400 degrees C. The results show that these polymers may be arranged in the following order of increasing thermostability : CN < CP < regenerated cellulose < filter cotton < CDA < CTA. The activation energy (E), order (n), and frequency factor (Z) of their degradation reactions were obtained following the Friedman, Chang, Coats-Redfern, Freeman-Carroll, and Kissinger methods. The dependence of T-d, T-dm, E, n, Ln Z, and char yield at 400 degrees C on molecular weight and test atmosphere is also discussed.