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Because of the instability of various fatty acids, enzymatic synthesis of esters seems to have advantages over the chemical production thereof. However, a mixture of products and substrates is obtained at equilibrium. In this paper, enzymatic acylglycerol synthesis is discussed with regard to equilibrium concentrations in a non-ideal two-phase system. The equilibrium constants for the different esterification steps are calculated using the UNIFAC group contribution method. The activity based equilibrium constants approximate one. Once the equilibrium constants are known, equilibrium concentrations can be predicted under different conditions using the program TREP (Two-phase Reaction Equilibrium Prediction). It is shown that in a two-phase system with decanoic acid and hexadecane as solvent a mixture of mono-, di- and triester is always obtained without a considerable surplus of any of these. Calculations show that, even with a high glycerol to fatty acid ratio, no pure monoesters can be obtained. Pure triester synthesis can be achieved only under conditions of low water activity.