In the present work, the liquid-liquid phase equilibrium data for the glycerol-methanol-methyl oleate and glycerol-monoolein-methyl oleate ternary systems were determined experimentally and compared with predictions of the UNIFAC and UNIFAC-Dortmund models. Liquid two-phase multicomponent systems consisting mainly of these chemical species are found in some industrially important transesterification reactions. For the glycerol-methanol-methyl oleate ternary system at 60 degrees C, the predictions of UNIFAC and UNIFAC-Dortmund are in good agreement with the experimental results. For the ternary glycerol-monoolein-methyl oleate system at 135 degrees C, the predictions of UNIFAC and UNIFAC-Dortmund deviate significantly from the experimental data and are only qualitatively correct. The reliability of the experimental data was determined through Othmer-Tobias plots.