Liquid-liquid equilibrium (LLE) data have been measured for one ternary system of water + N-methyl-2-pyrrolidone + I-pentanol, and three quaternary systems of water + N-methyl-2-pyrrolidone + 1-pentanol + sodium chloride, +potassium chloride, or +potassium acetate at temperatures 283.15 and 323.15 K under atmospheric pressure. The liquid-phase splitting for ternary system of water + N-methyl-2-pyrrolidone + 1-pentanol can be enhanced by adding the same percentage of salts (sodium chloride, potassium chloride, or potassium acetate) and the influence follows the order of sodium chloride > potassium chloride > potassium acetate. The experimental data were also compared with the values calculated by the Electrolyte-NRTL model. In general, the model reproduces reasonably for the LLE phase diagrams. (c) 2008 Elsevier B.V. All rights reserved.