PURPOSE: To surely obtain useful pharmaceuticals, etc., by reacting 9,10- dihydroxystearic acid with a sterol in the presence of a lipase and purifying the reaction product.

CONSTITUTION: (A) 9,10-Dihydroxystearic acid is compounded with (B) a sterol in the presence of (C) a lipase originated from Mucoa miehei, etc., at a molar ratio (C:A) of 1:(0.1-1.0) and the mixture is incorporated with (D) 1-15 pts.wt. (based on 1 pt.wt. of the component A) of a solvent such as cyclohexane to obtain a reaction mixture (E). The mixture E is subjected to esterification reaction for 30min to 8hr. After the completion of the reaction, the solvent is removed under reduced pressure and the residue is purified by silica gel column chromatography to recover the objective 9,10-dihydroxystearic acid sterol ester of formula (R is 27-29C sterol residue).