The synthesis of tricaprylin, tricaprin, trilaurin, and trimyristin in a solvent-free system was conducted by mixing a commercial immobilized lipase (Lipozyme IM 20, Novo Nordisk, Bagsvaerd, Denmark) with the organic reactants (glycerol and fatty acids) in a 20-mL batch reactor with constant stirring. In a first set of experiments, the effect of water concentration (0-6%) on the reaction conversion was shown to be negligible. In a second set of experiments, the effects of temperature (70-90 degrees C), fatty acid/glycerol molar ratio (1-5), and enzyme concentration (1-9% [w/w]) on the reaction conversion were determined by the application of a 3 x 3 experimental design. The reactions were carried out for 26 h and the nonpolar phase was analyzed by gas chromatography (GC). Appreciable levels of medium-chain triglycerides were achieved, except for tricaprylin. For the triglyceride production, higher selectivity was attained under the following conditions: molar ratio of 5, enzyme concentration of 5 or 9% (w/w) and temperatures of 70 degrees C (tricaprin), 80 degrees C (trilaurin), and 90 degrees C (trimyristin). Statistical analysis indicated that the fatty acid/glycerol molar ratio was the most significant variable affecting the synthesis of triglycerides.