The boron trifluoride-catalyzed cationic copolymerization of epichlorohydrin and glycidol is examined in some detail, with reference to the effect of various reaction variables such as temperature, water content, and stirring rate on the polymerization process and the copolymer product. The reaction temperature does not have a strong effect on the molecular weight of the copolymer, but the water content of the reaction mixture is inversely related to the molecular weight. The stirring rate strongly affects the exotherm associated with the initial stages of the reaction : improved stirring diminishes the exotherm. Based on the relative rates of monomer consumption and other observations, a reaction mechanism is proposed for the formation of the copolymer, in which glycidol polymerizes via what is known as the activated monomer (AM) mechanism rather than by the standard cationic ring-opening polymerization mechanism.