The present report describes the further development of a novel experimental route to the four independent components of the anisotropic electric dipole polarizabilities of molecules of C, symmetry, originally applied to CH3NH2 and (CH3)(2)NH [Ritchie, G. L. D.; Blanch, E. W. J. Phys. Chem. A 2003, 107, 2093-2099] and here extended to CH3CH2CN and (CH3)(2)CHCN. Once again, the four equations required to evaluate the four components of the optical-frequency (lambda = 632.8 nm) polarizabilities are drawn from observations of (1) the temperature dependence of the electrooptical Kerr effect, (2) the Rayleigh depolarization ratio, and (3) the refractive index of the gas, together with (4) a simple bond-additivity model of the polarizability. Although the measurements are difficult and still much less than routine, the procedure is applicable to many other species of this symmetry, for which free-molecule anisotropic polarizabilities have not previously been experimentally accessible.