Liquid-liquid equilibria of the ternary systems {cyclohexane + benzene + N-methyl formamide} and {cyclohexene + benzene + N-methyl formamide} were measured at temperatures of (288.15, 298.15, and 308.15) K. The results were predicted using the UNIQUAC equation with dimensionless parameters (T-ij) which were related to linear functions of the reciprocal of temperature. The total average deviations of three temperatures between the predicted and experimental values were estimated as 0.92% for the former system, and as 0.87% for the latter one.