We report the ring-opening homopolymerization of a-allyl(valerolactone), compound 2, and its copolymerization with epsilon-caprolactone and delta-valerolactone using stannous(II) catalysis. Although the polymerization of substituted delta-valerolactones has received little attention for the preparation of functional polyesters, we found that compound 2 may be incorporated in controllable amounts into copolymers with other lactones, or simply homopolymerized to give a highly functionalized, novel poly(valerolactone). The presence of the pendant allyl substituent had a substantial impact on the thermal properties of these materials relative to conventional polyesters prepared from lactones, and most of the polymers presented here are liquids at room temperature. Dihydroxylation of the pendant allyl groups gave polyesters with increased hydrophilicity that degraded more or less rapidly depending on their extent of functionality.