Some dielectric, refractive index and far infrared data on cholesteryl oleyl carbonate (OCC) in the smectic, cholesteric and isotropic liquid phases are reported. The molecular dipole moment is 3.80 × 10–30 C m (1.14 D) and the molecular polarizability ellipsoid nearly spherical. Dielectric relaxation studies show that the enthalpy of activation for molecular reorientation is (70 ± 20) kJ mol–1 in the isotropic phase, (44 ± 20) kJ mol–1 in the cholesteric phase and (35 ± 20) kJ mol–1 in the smectic phase and involves the reorientation of the “lath”-like molecule probably about a lengthwise axis. A broad absorption is observed at 78 cm–1 in the far infrared region in the chloesteric mesophase. This is assigned to a libration of the cholesteric framework about a lengthwise axis. Quantitative aspects suggest that the mean barrier to libration in the mesophase is about 17.3 kJ mol–1.