Excess molar enthalpies H-m(E) for {xC(3)H(8) + (1 - x)C2H6) have been measured over the entire composition range except at the mole fraction extremes, at p=(5, 10, and 15) MPa and T=(273.15, 298.15, 323.15, 348.15, 363.15, 369.82, and 373.15) K. Measurements were also made al p = 12.5 MPa and T = (273.15 and 369.82) K; at p = 7.5 MPa and T = (273.15, 348.15, and 369.82) K; and at p = 6 MPa and T= 323.15 K. The critical pressures and temperatures are p(c) = 4.25 MPa and T-c = 369.82 K for propane, and p(c) = 4.91 MPa and T-c = 305.50 K for ethane. Thus, measurements were made at two temperatures where both components are liquid {T=(273.15 and 298.15)K}, at three temperatures where one component (C3H8) is a liquid while the other (C2H6) is a supercritical fluid jT = (323.15, 348.15? and 363.15) Kj, a temperature (T= 369.82 K) at or very near the critical temperature of the propane and well above the critical temperature of ethane, and al one temperature where both components are supercritical fluids (T = 373.15 K). Excess molar volumes V-m(E) were measured at T= 323.15 K with p = 10 MPa, and at T= (348.15 and 363.15)K with p = (5, 10, and 15) MPa. At T = (273.15 and 298.15) K (where both components are liquid), the H-m(E) values are small and < O, with positive pressure coefficients. At T = 298.15 K, H-m(E) is more negative al each pressure than at T= 273.15 K, although small compared with the Hf values at higher temperatures where supercritical fluids are present and large maximum and minimum values of H-m(E) and V-m(E) are obtained that are very temperature and pressure-dependent. The effects of pressure and temperature and the shape of H-m(E)(x) and V-m(E)(x) are explained as resulting from major contributions from condensation and vaporization terms, especially when supercritical ethane is mixed with liquid propane. The H-m(E) results for this system are compared with those for the related hydrocarbon mixtures (propane + ethene) and (ethane + ethene). Comparisons are also made with (ethane + chloromethane), (ethane + acetonitrile), and (ethane + methanol),in which the ethane is mixed with liquids of varying polarities.