New experimental isothermal P, x, y data for the ternary systems dibutyl ether + cyclohexane + heptane and dibutyl ether + cyclohexane + I-hexene and for the binary systems dibutyl ether + 1-hexene and dibutyl ether + heptane at 313.15 K are reported. Data reduction by Barker's method provides correlations for G(E), using the Margules equation for the binary systems and the Wohl expansion for the ternary systems. Wilson, NRTL, and UNIQUAC models have been applied successfully to both of the binary and ternary mixtures presented here.