AbstractEpoxides, propylene oxide in particular, were polymerized by a catalyst system consisting of AlEt3–metal soap, to high molecular weight polyethers in high conversion. Carboxylic acid salts of Ti, V, Cr, Zr, Mo, Co, and Ni, transition metals of groups IV–VIII in the Periodic Table, were most preferable. Metal salts of stearic, octanoic, lauric and naphthenic acid were examined as catalyst components and proved to be very active for the polymerization of epoxides when used with an organoaluminum compound such as AlEt3or AlEt2Cl. Copolymerization of propylene oxide and allyl glycidyl ether was successfully carried out with an AlEt3–Zr octoate cat