Electro-optical properties of solutions of several cellulose esters in dioxan have been investigated. It was shown that macromolecules of the esters display high equilibrium and kinetic chain rigidity. The coincidence of the Kerr and Maxwell effects in solutions of the samples reveals general relationships exhibited by all rigid chain polymers for which the longitudinal geometric axis of the molecule (direction of the greatest geometric length) is also the symmetry axis of its polar and optical properties.