Co(II) and Mn(II) salts were assessed to be good catalysts for the bulk ring-opening polymerization of cyclic esters. These polymerizations are reasonably controlled leading to the formation of polymer with good number average molecular weights (M n) and narrow molecular weight distributions. The polymerizations were studied in the presence and absence of benzyl alcohol and the polymerization tendency was found to increase in the presence of benzyl alcohol. The polymerization proceeds through the activated monomer mechanism, resulting in the formation of polymers containing the initiator as one of the end terminal groups. All the polymerizations show first-order kinetics with respect to monomer concentration. Ease of handling and low cost of Co(II) and Mn(II) salts make the catalytic process economically attractive. © 2014 Springer-Verlag Berlin Heidelberg.