Liquid-liquid equilibrium (LLE) for the quaternary system propionic acid + n-propanol + n-propyl propionate + water and for the ternary sub-systems propionic acid + n-propyl propionate + water and n-propanol + n-propyl propionate + water were studied at 293.15, 313.15 and 333.15 K and atmospheric pressure. Binodal surface in quaternary system and binodal curves in ternary systems were determined. Experimental LLE data were compared with the values calculated by NRTL models, these data are in good agreement. (C) 2016 Elsevier B.V. All rights reserved.