Poly(p-dioxanone-co-ethyl ethylene phosphate)s were successfully synthesized by the ring-opening copolymerization of p-dioxanone and ethyl ethylene phosphate with triisobutyl aluminum as an initiator; this was confirmed by H-1-NMR and infrared spectra. The effects of the reaction conditions, such as the feeding ratio of the monomers and the reaction temperature and time, on the molecular weight of the copolymers were also studied. The in vitro degradation results showed that the introduction of phosphate segments into the backbone chains of the copolymers led to an enhancement of the degradation rate of the copolymers. (c) 2006 Wiley Periodicals, Inc.