Liquid-liquid equilibrium (LLE) for the quaternary system acetic acid-n-butanol-n-butyl acetate-water and for the ternary sub-systems acetic acid-n-butyl acetate-water, n-butanol-n-butyl acetate-water and acetic acid-n-butanol-water were studied at 308.15 K and atmospheric pressure. Binodal surface and curves, tie-lines and compositions of critical points of LLE were determined. Experimental LLE data were correlated by NRTL model. Experimental LLE data were compared with the values calculated by NRTL models, these data are in good agreement. (C) 2014 Elsevier B.V. All rights reserved.