A static VLE apparatus has been used for the measurement of the (vapour+liquid+liquid) equilibrium of the (propylene+isopropanol+water) system at T=313.15K and pressures between (1.381 and 1.690)MPa. Using an isothermal flow calorimeter, HE values have been obtained for the binary system (isopropanol+water) over the temperature range from (313.15 to 353.15)K and pressures from (3.8 to 4.19)MPa. For the pseudo-binary mixture (propylene+(isopropanol+water)), HE values have been measured in the temperature range from (313.15 to 353.15)K and pressures from (1.997 to 5.89)MPa. This last mixture was studied starting from (isopropanol+water) at 0.25, 0.50, and 0.75 molar compositions in isopropanol. The new data, together with the available phase equilibrium and HE data from the literature, have been regressed by a conventional GE–EoS model reaching satisfactory results, except for the VLLE representation.