High molecular weight poly(alpha-methyl beta,L-malate) (M-n similar to 25,000, PD similar to 1.7) was prepared from microbial poly(beta,L-malic acid) (M-n similar to 29,000, PD similar to 1.3) by methylation with diazomethane in dry acetone without substantial cleavage of the polyester main chain. The thermal properties of this poly(malate) were assessed and its crystal structure was preliminary examined. Two crystal forms were identified by X-ray diffraction, their occurrence being dependent on crystallization conditions. The kinetics of nonisothermal and isothermal crystallizations from the melt were studied and modelled using the Avrami approach. Results were compared to those recently reported by us for low molecular weight poly(alpha-methyl beta,L-malate) (M-n similar to 3000, PD similar to 1.3). (c) 2006 Published by Elsevier Ltd.