(Liquid + liquid) equilibrium data are presented for (acetonitrile + acetic acid, or propanoic acid, or butanoic acid, or 2-methylpropanoic acid, or pentanoic acid, or 3-methylbutanoic acid + cyclohexane) at T = 298.15 K. The relative mutual solubility of each of the carboxylic acids is higher in the acetonitrile layer than in the hydrocarbon layer. The influence of 3-methylbutanoic acid, pentanoic acid, 2-methylpropanoic acid, and butanoic acid on the solubility of the hydrocarbons in acetonitrile is greater than that of acetic acid and propanoic acid. Three there-parameter equations have been fitted to the binodal curve data. These equations are compared and discussed in terms of statistical consistency. The NRTL and UNIQUAC models were used to correlate the experimental tie-lines and to calculate the phase compositions of the ternary systems. The NRTL equation fitted the experimental data far better than the UNIQUAC equation. Selectivity values for solvent separation efficiency were derived from the tie-line data.