Regioregular poly(propylene oxide), PPO, formed by simple base (KOH) and coordinate base (TPP)AlCl, (tetraphenylporphinato)aluminum chloride, ring-opening polymerization of propylene oxide, PO, has been studied by high field C-13{H-1} NMR spectroscopy at various concentrations in CDCl3 and C6D6. The original assignments of Tonelli and Schilling [Macromolecules 1986, 19, 1337-1343] at the triad and diad sensitivity level have been extended to tetrad sensitivity.