Epilactose (4-O-beta-galactopyranosyl-D-mannnose) is a rare disaccharide in cow milk that can be synthesized from lactose by the cellobiose 2-epimerase of Ruminococcus albus. Epilactose is a promising prebiotic. Dietary supplementation with epilactose (4.5%) increased cecal wall weight and cecal contents and decreased the pH of the cecal contents in Wistar-ST rats. The number of total anaerobes tended to be greater in rats fed epilactose than in those fed the control diet. Epilactose inhibited the conversion of primary bile acids to secondary bile acids. Epilactose also increased the calcium absorption in everted small intestinal sacs. In addition, the levels of plasma total cholesterol and nonhigh-density lipoprotein cholesterol were lower in epilactose-fed rats. These results indicate that epilactose promotes calcium absorption in the small intestine and possibly lowers the risk of arteriosclerosis.