Density measurements have been carried out by means of a vibrating tube densimeter for the ternary system ethanol (EtOH) + dimethylformamide (DMF) + tetrahydrofuran (THF) and for the binary mixtures containing DMF. For the same ternary system and for the binary DMF + THF vapour-liquid equilibrium data have been collected by head-space gas-chromatographic analysis of the vapour phase directly withdrawn from an equilibration apparatus. All experiments have been conducted at 298.15 K. Molar excess Gibbs energies G(E) and volumes V-E, as well as activity coefficients gamma(i) and excess apparent molar volumes Phi(E)(V,1) of the components, have been obtained from the measured quantities. Both binaries involving THF show positive deviations from ideality for G(E), while slightly negative deviations are exhibited by EtOH + DMF. The G(E)'s and In gamma(i) of the ternary system are positive almost throughout due to destruction upon mixing of H-bonding in EtOH and dipolar interactions in DMF and THF pure liquids. Feeble negative V-E's are displayed by the binaries involving DMF, whereas EtOH + THF shows an S-shaped curve with very small V-E values. As a consequence, the VE's and Phi(E)(V,1) of the ternary system, differently from G(E) and In gamma(1), are negative nearly over the whole composition domain suggesting a more ordered structure in solution, namely that EtOH-DMF association prevails on EtOH and DMF self-association. (C) 2013 Elsevier B.V. All rights reserved.