Isobaric vapour-liquid equilibrium measurements for mixtures containing tetrahydropyran and isomeric chlorobutanes at 40.0 and 101.3 kPa are reported and studied using two thermodynamic approaches: y-phi and phi-phi. Activity coefficients were calculated from experimental data, previously the thermodynamic consistency of the VLE measurements has been checked with the van Ness test. Wilson, NRTL, and UNIQUAC models have been used to correlate the activity coefficients. On the other hand the Peng-Robinson-Stryjek-Vera equation of state using the Wong-Sandler mixing rules has been also used to predict the vapour-liquid equilibrium for these mixtures. (c) 2005 Elsevier B.V. All rights reserved.