The degradation and glass transition temperatures of a series of methyl methacrylate (MMA)-ethyl alpha-hydroxymethylacrylate (EHMA) copolymers have been studied by t.g.a./i.r. and d.s.c. Thermal degradation yielded intramolecular lactone and intermolecular crosslinking formation, with concurrent loss of ethanol and/or methanol involving adjacent or near-neighbour EHMA or MMA units. Glass transitions of copolymers have been analysed as a function of sequence distribution and their values compared to the theoretical ones derived using Johnston’s equation. The partially degraded copolymers increased their glass transition temperatures as a consequence of the above mentioned lactone and crosslinking formation.