A three-variable theory of anisotropic relaxation, closely related to one previously described for VH depolarized light scattering, is described and applied to flow birefringence. The anisotropic dielectric fluctuations in liquids are described in terms of orientational and stress tensor (intermolecular) fluctuations. Even in liquids composed of symmetric top molecules, the intermolecular contributions to flow birefringence are predicted to be significant. Using the parameters obtained from light scattering, we calculate the stress-optical coefficient for triphenylphosphite over the temperature range 10–40 °C, and obtain approximate agreement with the values obtained from flow birefringence experiments. However, we find an appreciable discrepancy between the calculated and experimental temperature dependences.