The ring-opening copolymerization of 5-benzyloxy-trimethylene carbonate (BTMC) with trimethylene carbonate (TMC) was described. The polymerization was carried out in bulk at 150 °C using stannous octanoate as initiator. The influence of reaction conditions such as polymerization time and initiator concentration on the yield and molecular weight of the copolymers were investigated. The poly(BTMC-co-TMC)s obtained were characterized by FT-IR, 1 H NMR, 13 C NMR, GPC and DSC. NMR results of copolymer showed no evidence for decarboxylation occurring during the propagation. The relation- ship between the copolymer glass transition temperature and composition was in agreement with the Fox equation. The in vitro cytotoxicity studies of the poly(BTMC-co- TMC) (50:50) using 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay demonstrated that the copolymer has low cytotoxicity compared to poly[(lactic acid)-co-(glycolic acid)] (75:25).