Liquid-liquid equilibrium data are presented for mixtures of butanal + an alkanol + water at 298.15 K. The alkanols are methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and a-methyl-a-propanol. The addition of ethanol or 2-propanol or 2-methyl-2-propanol is found to increase the solubility of water in the butanal more than the others alkanols. The relative mutual solubility of alkanols is higher in the butanal layer than in the water layer. Three three-parameter equations have been fitted to points on the binodal curve. The results are compared and discussed in terms of statistical consistency. The NRTL and UNIQUAC models were used to correlate the experimental results and to calculate the phase compositions of the ternary systems. The NRTL equation fitted the experimental data better than did the UNIQUAC equation, and the average root mean square deviation phase composition error was 0.003 for the NRTL model and 0.089 for the UNIQUAC model.