Polymerization of delta-valerolactone has been stuidied using gamma-butyrolactone enolate as initiator. Mechanistic studies show that the initiation proceeds with incorporation of the initiator into the growing polymer chain and acyl-oxygen bond cleavage of the monomer. The molecular weight distribution of the resulting polymers is narrow compared to that of poly(delta-valerolactone) obtained from common anionic initiators, e.g. alkali metal alkoxides.