Excess molar enthalpies (H-E) at 318.15 K are reported for two ternary systems, o-xylene + cyclohexanol + phenol and o-xylene + cyclohexanol + 1,3-butanediol, and for two constituent binaries formed by o-xylene with phenol and 1,3-butanediol. The ternary system containing phenol exhibits regions of both exothermic and endothermic mixing, H-E for the other ternary system are endothermic. Owing to partial miscibility in the o-xylene + 1,3-butanediol system, the ternary system containing 1,3-butanediol includes a region with two coexisting liquid phases; A modified Redlich-Kister equation fitted to experimental results provides a satisfactory mathematical representation of H-E data for the o-xylene + cyclohexanol + 1,3-butanediol system.