Single crystals of poly(γ‐benzyl L‐glutamate) were formed by epitaxial crystallization from solution in mesitylene on NaCl, KI, and KCl (001) cleavage faces. From electron microscopy and diffraction studies, the structure of these overgrowths was determined to be that of lamellae containing chain‐folded α‐helical macromolecules. The usual type of crystal perfection, that of ordered helix axes and disordered side groups, was exhibited by this synthetic polypeptide. Unique orientation regimes were observed with each substrate. Copyright © 1968 John Wiley & Sons, Inc.