Lactase from Kluyveromyces lactis was found to have high transglucosylation activity, transferring the glucosyl group of aryl glucoside to an alcoholic hydroxyl group in high yield. Both primary and secondary alcohols can accept the glucosyl group. Transglucosylation to glycol yielded a single kind of glucoside. A very hydrophilic alcohol, such as glycerol, could not serve as a substrate in this system. Hydrophobic alcohols slightly soluble in water were glucosylated in a two-phase system consisting of water and an organic solvent immiscible with water.