We studied the performance of Fusarium solani pisi cutinase, immobilized on a zeolite, in supercritical fluids. The catalytic activity of the enzyme was strongly dependent on water activity, was unaffected by pressure up to 300 bar, and was higher in supercritical ethylene than in supercritical carbon dioxide. The enzyme was very selective toward one of the isomers of 1-phenylethanol, with an enantiomeric excess of virtually 100%, regardless of water activity, pressure, solvent, and temperature. We used the X-ray crystal structure of the enzyme and did a computer modeling of the structures of the transition states formed by the two enantiomers. The differences between these structures helped elucidate the preference for the (R)-enantiomer.