The quasi-living cationic copolymerization of 3,3-bis(chloromethyl)oxetane (BCMO) and epsilon-caprolactone (epsilon-CL), using boron trifluoride etherate as catalyst and 1,4-butanediol as coinitiator, was investigated in methylene chloride at 0 degrees C. The resulting hydroxyl-ended copolymers exhibit a narrow molecular weight polydispersity and a functionality of about 2. The reactivity ratios of BCMO (0.26) and epsilon-CL (0.47), and the T-g of the copolymers, indicate their statistical character. The synthesis of poly(3,3-bis(azidomethyl)oxetane-co-epsilon-caprolactone) from poly(BCMO-co-epsilon-CL) via the substitution of the chlorine atoms by azide groups, using sodium azide in DMSO at 110 degrees C, occurs without any degradation, but the copolymers decompose at about 240 degrees C. All polymers were characterized by vapor pressure osmometry or steric exclusion chromatography, H-1-NMR and FTIR spectroscopies, and DSC.