A sequential isochoric flash experiment is described for measurement of three-phase (VLL) equilibria for aqueous systems with one or more hydrocarbon components. Data are reported for a number of systems of interest in the thermal recovery of crude oil via steam distillation. A Peng-Robinson equation-of-state model is shown to provide reasonable a priori prediction of these measurements. Improved equations for prediction of the binary interaction constants k(ij) are presented for use with the van der Waals combining rules