AbstractTheDandLcopolymerizations ofN‐carboxy γ‐benzyl glutamate anhydride (NCA) were carried out in a homogeneous solution with variousD/Lratios, initiated by eithern‐butylamine or sodium methoxide, and were followed directly by circular dichroism (CD) to observe the behavior of the secondary structure of growing polymer molecules. In then‐butylamine system, the difference of the helical content between the righthanded and the lefthanded (Δα‐helix) gradually increased as the polymerization proceeded, while in the sodium methoxide system, the Δα‐helix had a tendency to decrease during the later stages of the polymerization. These results suggest a difference of the power of stereo‐selection of monomer antipodes by the growing chain end between these systems, the stereoselectivity by the growing chain end in the sodium methoxide system being higher than that in then