The conditions for the reduction of dibenzoyl by silicone-immobilizedGeotrichum sp. G38 were examined, and optimal concentrations of stannous octanoate, ethyl silicate, water and entrapped biomass for the reaction were established. The optimum pH and temperature of the reaction medium were 7.0, and 35‡C (free cells) or 40‡C (immobilized cells), respectively. The immobilized cells showed higher activity than free cells under optimum conditions. The extent of conversion remained greater than 90% even after immobilized cells had been recycled 28 times. When silicone-immobilizedGeotrichum sp. G38 was used in the reduction of ethyl benzoylacetate, the (R)-enantiomer was obtained in an 81% enantiomeric excess compared with 49% enantiomeric excess using free cells.