The temperature variation of refractive indices (ne,no), birefringence (n), density (), and order parameter of the homologous compounds trans-4-alkyl (4-cyanophenyl)-cyclohexane are reported in the nematic and isotropic phases. The principal molecular polarizabilities (e,o) and the order parameters S have been evaluated using the anisotropic internal field model (Neugebauer's approach). The theoretical estimations of the mean and principal molecular polarizabilities made by two different approaches, viz., the additivity rule of bond polarizability and the modified Lippincott--function potential model are in close agreement with the values evaluated from the experimental studies. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.