Measurements have been made of the Kerr constants and dipole moments at infinite dilution in CCl4for endo-5-cyanonorbornene, exo-5-cyanonorbornene, 5-chloronorbornene, and 5-bromonorbornene. These quantities are used with the molar Kerr constant, degree of depolarization of the scattered light, and the dipole moment of cyclohexene to calculate the axes of the polarizability ellipsoid for the C=C bond: bL(along the bond), bT(in plane of bond), and bV(perpendicular to that plane).