A positive correlation between refractive index and density has been experimentally illustrated in the literature for numerous materials, including polymers. This relationship was exploited in an attempt to follow the densification of a glassy polymer during the physical aging process. Atactic polystyrene films were aged at 74 degrees C and the refractive index (n) was evaluated as a function of aging time (t(a)) using an Abbe refractometer. The refractive index increased linearly with respect to log (t(a)), and this dependence was used in conjunction with experimentally determined values of the thermal expansion coefficient in the glassy state and (delta n/delta T)(P,ta) for unaged polystyrene to determine the volume relaxation rate at 74 degrees C. This rate was similar to that obtained for the same polystyrene material using a precision dilatometer, indicating the possibility for using refractive index measurements to quantitatively assess volume relaxation during physical aging.