A flow-mixing calorimeter has been used to measure the excess molar enthalpy H-m(E) Of (cyctohexane + diethyl ether)(g) and (benzene + diethyl ether)(g) at standard atmospheric pressure over the temperature range 353.2 K to 423.2 K. The non-ideality of the cyclohexane and benzene was fitted using the Kihara potential, and that of the diethyl ether using the Stockmayer potential. Cross-terms were calculated using the equation epsilon(12) = (1 - k(12))(epsilon(11)epsilon(22))(1/2) and to fit the measurements on (cyclohexane + diethyl ether)(g) the value (1 -k(12)) = 0.97 was needed. This value was used to calculate H-m(E) for (benzene + diethyl ether)(g), but the experimental values were found to be about 10J . mol(-1) less positive. The difference between the calculated and experimental values was described in terms of a quasi-chemical model which, for the benzene-diethyl ether interaction, yielded a value of the equilibrium constant K-12(298.15 K) = 0.099 MPa-1, and an enthalpy of association Delta H-12 = -(9.5 +/- 3) kJ . mol(-1). This value of Delta H-12 is attributed to dipole-quadrupole and quadrupoele-quadrupole forces which are stronger for the benzene-diethyl ether interaction than for the cyclohexane-diethyl ether interaction.