This article described the synthesis of cyclic poly(epsilon-caprolactone) (PCL) via ring-closing metathesis (RCM), ring closing enyne metathesis (RCEM), and "click" reaction of difrerent difunctional linear PCL. Linear PCL precursors were prepared by ring-opening polymerization (ROP) of epsilon-caprolactone in bulk using 10-undecen-1-ol or propargyl alcohol as the initiator, followed by reacting with corresponding acyl chloride containing vinyl or azido end group. The subsequent end-to-end intramolecular coupling reactions were performed under high dilution conditions. The successful transformation of linear PCL precursor to cyclic PCL was confirmed by Gel permeation chromatography, H-1 NMR, and Fourier transform infrared measurements. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3022-3033, 2009