Liquid-liquid equilibrium data are reported fdr the water + 4-hydroxy-4-methyl-2-pentanone + benzyl alcohol ternary system at 298.15 K. Data for the binodal curve have been determined by the cloud-point method. Tie lines were established by correlating the refractive index of the binodal curve as a function of composition and were satisfactorily correlated by the Othmer and Tobias method on a mass-fraction basis. In addition, density, viscosity, and refractive index isolines were obtained throughout the miscible region at 298.15 K. From the experimental densities and-viscosities, molar excess volume and viscosity deviations from a mole fraction average were calculated for the ternary system. The extracting capability of benzyl alcohol for separating 4-hydroxy-4-methyl-2-pentanone from its aqueous solutions was investigated in terms of distribution coefficients and selectivities. It is concluded that benzyl alcohol is appropriate for this extraction process when the mass fraction of the consolute component in the extract phase is smaller than 0.22, but it is less appropriate when this concentration is greater.