Vapour pressures of di-n-propylether + l-propanol or + 2-propanol at eight temperatures between 278.15 and 323.15 K were measured by a static method, Excess molar enthalpies and volumes were also measured at 298.15 K. Following Barker's method, the activity coefficients and the excess molar Gibbs free energies were fitted to the Wilson equation. Azeotropic mixtures with a minimum boiling temperature were observed over the whole temperature range.