Consistent vapor-liquid equilibrium (VLE) data at 101.3 kPa have been determined for the ternary system dipropyl ether (DPE) + 1-propanol (PA) + 1-pentanol and two constituent binary systems: DPE + 1-pentanol and PA + 1-pentanol. The DPE + 1-pentanol system shows positive deviations from ideal behaviour and PA + 1 -pentanol system exhibits no deviation from ideal behaviour. The activity coefficients and the boiling points were correlated with their compositions by the Wilson, NRTL, UNIQUAC and Wisniak-Tamir equations. It is shown that the models allow a very good prediction of the phase equilibria of the ternary system using the pertinent parameters of the binary systems. I-Pentanol eliminates the DPE-PA binary azentrope. The change of phase equilibria behaviour is significant therefore this solvent seems to be an effective agent for the separation of the azeotropic mixture by extractive distillation. (c) 2006 Elsevier B.V. All rights reserved.