Abstract: Proteases originating from Aspergillus melleus (Protease P) and Bacillus subtillis (Prolether FG-F) were entrapped into organic-inorganic hybrid silicates on Celite 545 by the sol-gel method, and their activities measured at 35degreesC for transesterification of chiral glycidol with vinyl n-butyrate in isooctane. n-Butyl- and dimethyl-substituted silicates provided 12.6 times higher activities with Protease P and 5.5 times with Prolether FG-F, respectively, than those deposited on Celite 545. Although pretreatment of those immobilized proteases with the chiral glycidol affected transesterification activities of both enantiomers, the ratio of the initial transesterification rate of (S)-(-)-glyci.dol to that of (R)-(+)-glycidol, remained unchanged