Excess second virial coefficients of xenon + ethane mixtures were measured at eight temperatures between 205 and 273 K. A new differential apparatus, suitable to perform direct measurements of the excess second virial coefficient, E, is described. One important improvement over previous reports was the design of the thermostated cell. Values are reported at 10 K intervals. They are small and positive and decrease with increasing temperature. The resulting data were fitted to a simple polynomial function in inverse temperature. This equation and its derivative were used to evaluate the excess enthalpy and excess molar volumes of the gaseous mixture. Our results were compared with the data of Bell et al.