Potassium hydride with 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) was used in the anionic polymerization of (butoxymethyl)oxirane. Polymers with low ratio of mass- to number-average molar masses (<(M)over bar (w)>/<(M)over bar (n)> < 1.1) were obtained, each macromolecule being terminated (after hydrolysis) with a hydroxyl group on both of its ends. Chain transfer reactions to the monomer were not observed to operate in this system.