Ring-opening polymerization of omega-pentadecalactone (PDL) by tetrahydroborate complexes of rare earth metals, Ln(BH(4))(3)(THF)(3) (Ln = La (1), Nd (2), Y (3)), was studied. These complexes showed high activity for PDL polymerization in THF at 60 degrees C. Among the complexes 1-3, the neodymium complex 2 was most active. The obtained poly(PDL) was demonstrated to be hydroxytelechelic by (1)H-NMR and MALDI-TOF MS spectroscopy. Biodegradation of the poly(PDL) in compost at 60 degrees C was investigated, where 18% weight loss of the samples was observed after 280 days. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 2098-2103, 2011