The relative permittivity of pyrene-2,4-dinitrofluorobenzene, -2,4-dinitrochloro-benzene, -2,4-dinitrotoluene, -2,4-dinitrophenol complexes, and fluoranthene-2,4-dinitrophenol complex increases abruptly upon the polymorphic transition. The molar polarization measured below the transition temperature agrees with the molar refraction except for the second complex which shows a marked positive deviation. The dipole moment of the acceptor molecules in the high-temperature form was calculated on the assumption that the rotational freedom around the axis perpendicular to the ring plane gives rise to the orientation in an externally applied electric field and was found in good accordance with the literature or estimated value.