We have performed a first-principles study of the zone-center optical modes of hexagonalBaTiO3,showing that all the experimentally relevant low-energy modes are characterized by the same local polar distortions that determine the ferroelectric instability of the cubic perovskite. The influence of the particular stacking of theTiO6groups in the hexagonal structure and the occurrence of previously unreported low-energy Rigid Unit Modes are addressed. ©2000 American Institute of Physics.