(Ternary liquid + liquid) equilibria (tie-lines) of (water + acetone + a-pinene) at T= (288.15, 298.15, and 308.15) K and (water + acetone + beta-pinene, or limonene) at T = 298.15 K have been measured. The experimental (ternary liquid + liquid) equilibrium data have been correlated successfully by the original UNIQUAC and modified UNIQUAC models. The modified UNIQUAC model reproduced accurately the experimental results for the (water + acetone + a-pinene) system at all the temperatures but fairly agreed with the experimental data for the (water + acetone + p-pinene, or limonene) systems. (C) 2010 Elsevier Ltd. All rights reserved.