The esterification of palmitic acid with ethanol was investigated at various temperatures (3570 degreesC) in the presence of three lipases (Novozym 435, Lipolase 100T, and hog pancreas lipase) in supercritical carbon dioxide (SCCO2) and under solvent-free conditions. All enzymes showed an optimum temperature of 55 degreesC under both conditions. The effect of water and ethanol addition on the esterification of acid was also investigated. The conversion obtained in SCCO2 and under solvent-free conditions with Novozym at optimal conditions was 74 and 97%, respectively. Although a higher apparent yield was obtained under the solvent-free conditions due to higher substrate and enzyme concentrations, the reaction in supercritical carbon dioxide is better because of lower enzyme loading, higher reaction rates and easier downstream processing.