Novel double-metal cyanide (DMC) complex catalysts were prepared with various precursors of cobalt or nickel and zinc with potassium cyanide. In the presence of an alcohol initiator, but in the absence of an organic-binding ligand, the catalysts were highly active for the polymerization of alkyl-or alkenyl-substituted epoxides to produce poly(ether polyol)s. The polymer obtained from propylene oxide showed a more isotactic structure than did the polymer made from nonselective conventional catalysts. T e influence of different reaction variables were examined, including the ratio of the initiator to the substrate, the presence of a protonic agent, the temperature, as well as the concentration of the catalyst and the solvent.