The kinetics of thermal degradation of three vinyl chloride-co-vinyl acetate (PVC-co-PVAc) copolymers with PVAc content of 14, 14 and 10 wt.% was investigated at various temperatures (220-250 °C) in solution. Reaction samples were analyzed by gel permeation chromatography (GPC) to obtain the molecular weight distribution (MWD). The degradation rate coefficients were determined from the time evolution of the MWDs. The energies of activation, determined from the temperature dependence of the rate coefficients, of the three copolymers were 92, 77 and 100 kJ/mol, respectively. The degradation of these copolymers was also investigated thermogravimetrically in the presence of nitrogen. The activation energies, determined from the Friedman technique, were 114, 92 and 131 kJ/mol, respectively. This indicated that the overall stability order of the copolymers remained same in both the methods. This also indicated that copolymers having the same PVAc content exhibit different stability. To our knowledge, this is the first paper that reports the activation energies, rate coefficients for the degradation of these copolymers as well as show that copolymers having the same composition degrade differently. © 2002 Elsevier Science Ltd. All rights reserved.