The thermal degradation behavior of copolymers of methacrylic acid (81.5-61.9 mol %) and ethyl acrylate (EA) (38.1-17.4 mol %) was studied using thermogravimetry (TGA) and differential scanning calorimetry (DSC) and the degradation products were analyzed using mass spectroscopy and DSC-FTIR. From mass spectroscopy, it was observed that in the copolymers the main degradation products obtained below 280-degrees-C included water, ethanol, and methanol, whereas at higher temperature (up to 400-degrees-C), CO2, CO, and small olefins were liberated. Elimination of water and ethanol is attributed to anhydride formation, which is believed to result from two routes : (a) anhydride formation involving adjacent acid groups and (b) anhydride formation involving adjacent acid and ester groups. An endothermic transition in the DSC and percent weight loss in the TGA in the same temperature range (140-280-degrees-C) support the above proposal. An increase in weight loss with increase in EA content of the copolymer confirms the participation of EA in the anhydride formation.