The crystal structure of poly(co-pentadecalactone) (PPDL) synthesized by enzyme-catalyzed polymerization was determined by full-profile refinement. A pseudoorthorombic monoclinic unit cell with dimensions a = 7.49(1), b = 5.034(9), and c = 20.00(4)Angstrom (fiber axis), and alpha = 90.06(4) hosts two monomeric units belonging to polymer chains with opposite orientation, according to the P2(1) space-group symmetry. A close similarity to the crystal structure of poly(epsilon-caprolactone) was evident. However, the even number of backbone atoms in the monomer unit of PPDL leads to a lower crystal symmetry. (C) 2003 Wiley Periodicals, Inc.