Isothermal vapor-liquid equilibrium data at 333.15 K are reported for the ternary system di-n-butyl ether (DBE) + ethanol + toluene and for its subbinary subsystems DBE + toluene and ethanol + toluene by using headspace gas chromatography. The experimental ternary VLE data were correlated with the Wilson, NRTL and UNIQUAC models, and the binary VLE data were correlated with the same models. The excess molar volumes (V) and deviations in molar refractivity (Delta R) at 298.15 K for the same ternary and binary systems were also determined from measured densities (rho) and refractive indices (n(D)). The experimental V-E and Delta R data of the ternary system are correlated with Cibulka equation and the binary data were correlated with the Redlich-Kister equation. The ternary V-E and Delta R are additionally compared with estimated values using the contribution models of Tsao-Smith, Kohler, Rastogi and Radojkovic. (c) 2007 Elsevier B.V. All rights reserved.