In order to decrease the content of linoleoyl moiety in soybean oil, soybean oil that contains 22.8% oleoyl, 54.8% linoleoyl, and 7.1% alpha-linolenoyl moieties as molar acyl moiety composition was interesterified in hexane with oleic acid or alpha-linolenic acid, using an immobilized sn-1,3-specific lipase (Lipozyme(R) IM) from Mucor miehei. The reactions were carried out in a batch reactor at 37 degrees C in the following system : molar ratio of fatty acid to soybean oil = 1.0 similar to 6.0, 5.0 mt of hexane/500 mu mol soybean oil, and 10.0 or 15.0 batch interesterification units of enzyme/500 mu mol soybean oil. Under these reaction conditions, the rates of interesterification of acyl moieties in soybean oil were of the order : stearoyl > palmitoyl > linoleoyl > oleoyl > alpha-linolenoyl, and the reaction with oleic acid occurred without a significant loss of alpha-linolenoyl moiety. At the molar ratio of 3.0 and the reaction time of 6 h, triacylglycerols (TGs), which contain 50.8% oleoyl, 38.8% linoleoyl, and 5.4% alpha-linolenoyl moieties, were produced in the reaction with oleic acid; TGs that contain 13.5% oleoyl, 40.8% linoleoyl, and 40.4% alpha-linolenoyl moieties were obtained with alpha-linolenic acid. Approximately 86-88% of the interesterification of linoleoyl moiety, which occurred in 10 h, took place within 1 h.