Ternary solid-liquid equilibrium diagrams of the system methanol/carbamazepine (CBZ)/nicotinamide (NCT) were generated and are discussed in the range between 5 and 50 degrees C. A study of the phase diagrams reveals that co-crystals could successfully be prepared. An evaporative crystallization method was used to prepare the co-crystals. By increasing the temperature, the co-crystal solubilities increased. In most cases, the co-crystals formed near room temperature. Regions for co-crystal, CBZ + co-crystal, NCT + co-crystal, CBZ crystal, and NCT crystal formation, and for the saturated solution are visible in the ternary diagram. In the region of supersaturation of S > 2.2, co-crystals were formed.