Isobaric vapor-liquid-liquid equilibria (VLLE) were measured for the ternary system isopropenyl acetate + water + acetic acid at 101 kPa. The apparatus for determination of the VLLE was an all-glass dynamic recirculating still. The experimental data demonstrated the existence of a binary heterogeneous azeotrope at 353.05 K with a composition of 0.5269, 0.4731 mole fractions of isopropenyl acetate and water. The prediction of VLLE used the modified UNIQUAC model which was based on the experimental data includes binary VLE of isopropenyl acetate + acetic acid, binary VLE of water + acetic acid, binary LLE of isopropenyl acetate + water and a single tie-line of ternary LLE of isopropenyl acetate + water + acetic acid. Comparison of the experimental data and the calculated results was made, which shows a satisfactory fit of the thermodynamic model. (c) 2011 Elsevier B.V. All rights reserved.