Lipase catalyzed synthesis of epoxy-fatty acids from unsaturat-ed carboxylic acids was investigated. Under mild conditions unsaturated carboxylic acids were converted to peroxycarboxylic acids by lipase with hydrogen peroxide, then the unsaturated peroxycarboxylic acids epoxidised the C = C bond of themselves. Lipase catalyzed synthesis of epoxy-fatty acids from unsaturat-ed carboxylic acids was investigated. Under mild conditions unsaturated carboxylic acids were converted to peroxycarboxylic acids by lipase with hydrogen peroxide, then the unsaturated peroxycarboxylic acids epoxidised the C = C bond of themselves.