The synthesis, characterization, and some properties of new copolyesters analogous to poly(butylene terephthalate) (PBT), based on L-arabinaric and galactaric acids, are described. These copolyesters were obtained by polycondensation reaction in the melt of mixtures of methyl 2,3,4-tri-O-methyl-L-arabinarate or methyl 2,3,4,5tetra-O-methyl-galactarate and dimethyl terephthalate with 1,4-butanediol. Their weight-average molecular weights ranged between 10,000 and 34,000, with polydispersities ranging from 1.4 to 2.2. The composition of all the copolymers was analyzed by NMR, and was found to have a statistical microstructure. All these copolyesters were thermally stable, with degradation temperatures well above 300 degrees C. The melting temperature and crystallinity decreased in both series, and the glass transition temperature increased and decreased respectively, for the PBTGa and PBTAr series with increasing amounts of aldaric units in the copolyester chain. Only PBT-derived copolyesters containing a maximum of 30% aldaric units showed discrete scattering characteristic of crystalline material. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1168-1177, 2009