Copolymers of L-lactide (LLA), epsilon-caprolactone (CL), and ethylene glycol oligomer (EGO) were synthesized by ring-opening copolymerization of CL and LLA initiated by EGO at the LLA/CL molar ratios of 7/3, 5/5, and 3/7. The resulting viscous ternary copolymers (PLCE) with weight average molecular weight (M-w) ca. 3000 were reacted with maleic anhydride to give unsaturated group-containing copolymer (PLCEM) with M-w 6000-8000. The degree of unsaturation of PLCEM was 0.3-0.6 per one EGO block. The PLCEM was cured with benzoyl peroxide (BPO) to give a viscoelastic soft material insoluble in any solvent. The DSC analysis of the copolymers revealed that all the copolymers are amorphous materials having a glass transition temperature (T-g), which increased with increasing LLA/CL ratio. The crosslinked PLCEM showed a higher T-g than the corresponding PLCE and PLCEM. The crosslinked PLCEM showed good biodegradability, when measured by a BOD method using activated sludge. (C) 2004 Elsevier Ltd. All rights reserved.