The vapour pressures of liquid (3-diethylaminopropylamine (3-DEPA) + n-heptane) mixtures were measured by a static method between T = (303.15 and 343.15) K at 10 K intervals. The molar excess enthalpies H-E at T = 303.15 K were measured for the systems {3-DEPA + CnH2n+2 (n = 6, 7, 12)}. The molar excess Gibbs free energies G(E) were obtained with Barker's method and fitted to the Red-lich-Kister equation. The Wilson equation was also used. Deviations between experimental and predicted G(E) and H-E, by using group contribution UNIFAC (Gmehling version) model, were evaluated. (C) 2008 Elsevier Ltd. All rights reserved.