To investigate the substituent effects at the 3-O and 6-O positions on ring-opening polymerization, 3,6-di-O-benzyl-alpha-D-glucopyranose 1,2,4-orthopivalate (1), 3-O-benzyl-6-O-pivaloyl-alpha-D-glucopyranose 1,2,4-orthopivalate (2), 6-O-benzyl-3-O-pivaloyl-alpha-D-glucopyranose 1,2,4-orthopivalate (3), and 3,6-di-O-pivaloyl-alpha-D-glucopyranose 1,2,4-orthopivalate (4) were selected as starting monomers and were polymerized under various reaction conditions. It was concluded from the results of monomer 1 reported previously and from those of monomers 2-4 in our present study that the benzyl group at the 3-O position is indispensable for yielding stereoregular (1-->4)-beta-D-glucopyranan derivatives, i.e., cellulose derivatives. The mechanisms of ring-opening polymerizations are discussed.