The photorefractivity of a series of polymer liquid crystals that possess a 4-nitrobenzylideneaniline moiety or a cyanobiphenyl moiety as a mesogen and simultaneously as a nonlinear optical chromophore was investigated using two-beam coupling experiments. A large diffraction efficiency (eta) of 65% under application of a 37 V/mu m external electric field was obtained in the isotropic phase of a polymer liquid crystal mixed with charge transporting compounds. The photorefractivity was compared between the liquid crystalline polymers and amorphous polymers. The photorefractivity was found to be significantly enhanced in the isotropic phase of the liquid crystalline polymers compared to that of the amorphous polymers with almost the same molecular structure.