Characteristics of Candida rugosa lipase, which was entrapped in various alkyl-substituted organic silicates formed on Celite 545, have been investigated. The hybrid gel-entrapped lipase derived from an equimolar mixture of dimethyldimethoxysilane and tetramethoxysilane exhibited three times and ten times higher catalytic activity than deposited lipase on the same support at 35 degrees C and 75 degrees C, respectively. The enantioselectivity, defined as the ratio of the initial esterification rate of (-)-menthol to that of (+)-menthol, was increased with an increase in the chain length of the alkyl group and an increase in the number of the methyl group at 75 degrees C, whereas it remained virtually unchanged at 35 degrees C. The hydrophobic interaction between the lipase molecules and alkyl groups of the entrapping gel appeared to be a dominant factor for modification of the enzyme properties.