Esterification between oleic acid and oleyl alcohol, catalyzed by the Mucor miehei immobilized lipase in a batch-stirred tank reactor with supercritical carbon dioxide as solvent produced higher reaction rates at supercritical conditions than in the solvent-free system. A continuous fixed-bed reactor was designed based on the results obtained from batch experiments. At 150 bar, 40°C, and with water activity 0.46% w/w, the activity of the enzyme preparation is practically unchanged when CO 2 was used as solvent. The addition of small amounts of water increases the conversion rate. The higher conversion also was observed at longer residence time. When nbutane was used as reaction medium, a decrease in conversion was observed. JAOCS 72, 1345-1349 (1995).