Tungstophosphoric acid (HPW) and MCM-48-supported HPW catalysts are potential catalysts for the esterification of long-chain fatty acids and alcohols in supercritical CO2 medium even at low temperature (100 degrees C) and a short reaction period (6 h). The high performances of HPW in sc-CO2 medium are due to the effective mass transfer of reactants and products for the catalysis under the conditions. The yields of esters were enhanced with the increase in the chain length of acids and alcohols in the esterification in sc-CO2 medium. The MCM-48-supported HPW catalysts were active even after several recycle experiments.