The thermal degradation of the alternating copolymer of maleic anhydride and vinyl acetate has been studied by thermal volatilisation analysis (TVA). An investigation of the decomposition products and a comprehensive analysis of the residues have been made using subambient TVA, IR spectroscopy, 1H and 13CNMR spectroscopy, the GC-MS technique and UV spectroscopy. On the basis of this evidence, a mechanism of degradation has been suggested. Under programmed heating at 10°C min −1, two stages of breakdown, with rate maxima at 260 and 420°C, were observed. The products consisted of acetic acid, carbon dioxide, carbon monoxide, maleic anhydride and water. Acetic acid, carbon dioxide and traces of carbon monoxide were also observed in a detailed isothermal investigation at 205°C. It is suggested that, following the initial loss of acetic acid, structural rearrangements in the polymer chain can occur, with the formation of conjugated double bonds, so accounting for the colour of the partially degraded residues. Some hydroxyl groups are also formed. During degradation, insolubility develops, which has been attributed to reduction in the flexibility of the backbone and some intermolecular dehydration of OH groups. The interaction between the copolymer (or its residue) and water is discussed in relation to potential applications of this material.