Using commercial lipases immobilized in gels prepared from photo-crosslinkable prepolymers, n-alkenes (C-6-C-12) and cyclic alkenes (C-5-C-12) were converted to corresponding epoxides. Cyclooctene was converted most effectively with 54.5% of the maximum conversion by Candida cylindracea lipase immobilized in hydrophobic gel prepared from a photo-crosslinkable prepolymer, ENTP-4000. Substrates substituted with hydrophobic groups were epoxided, but the ones with hydrophilic groups were not epoxided.