The influence of solvents with a wide range of log P (from -0.23 to 4.5) on the positional selectivity of the immobilized lipase Novozym 435 during the esterification of oleic acid with glycerol for 1,3-diolein preparation was investigated. Analysis was performed on the basis of a simplified kinetic model of 1,3-diolein synthesis. The results showed that the preferential selectivity of Novozym 435 to 1-position over 2-position of the glycerol molecular became weaker and weaker with the increasing log P of the solvent. But after one 1-position was acylated, the preferential selectivity to the other 1-position over 2-position would be enhanced strongly for each solvent. The study also revealed that relatively hydrophilic solvent such as t-butanol was an ideal solvent for Novozym 435 catalyzed 1,3-diolein synthesis through esterification of oleic acid with glycerol. (C) 2009 Elsevier Ltd. All rights reserved.