The objective of this work was to determine liquid-liquid equilibrium data at (298.3 +/- 0.2) K for systems of interest in biodiesel production, such systems being composed of vegetable oils + anhydrous ethanol + hexane. The measurements were performed using near-infrared spectroscopy (NIR) for quantification of the phases in equilibrium. The following vegetables oils were investigated: pretreated cottonseed oil, corn oil, canola oil, refined soybean oil, and degummed soybean oil. Initially, with the,purpose of validating the NIR methodology, equilibrium data for the system composed of pretreated cottonseed oil (neutral) + commercial linoleic acid + anhydrous ethanol were determined at (298.2 +/- 0.1) K by a conventional method based on acid-base titration and solvent evaporation and by the NIR method. The relative errors between the phase compositions determined by both analytical methods were 2.1 % for the alcoholic phase and 2.0 % for the oil phase. The mass balance errors for all investigated systems varied in the range from 0.03 % to 0.16 %, which indicates the good quality of the experimental data and the good performance of the NIR method. The experimental data were correlated using the NRTL model with an average global deviation of 0.70 %.