Excess enthalpies (H-E) were determined for two ternary systems, o-xylene + cyclohexanol + nonane and 3-methylphenol + 1-hexanol + heptane, and for their constituent binaries at 298.15 K and for the first ternary system also at 318.15 K. The ternary H-E as a function of the composition was described by a new modification of the Redlich-Kister equation and presented in the form of isoenthalpic (H-E = const) curves.