This study was undertaken to investigate the hypocholesterolemic activity of Bifidobacteria (B. breve K-110, B. breve K-111, and B. infantis K-525) isolated from a healthy Korean. The administration of B. breve K-110 and K-111 with a high cholesterol diet significantly protected the increase of serum total cholesterol and LDL cholesterol relative to that of a high cholesterol diet alone. Such a diet supplemented with 0.5％ B. breve K-111 decreased serum total cholesterol and LDL cholesterol to 57 and 55％, respectively. The administration of Bifidobacteria also significantly inhibited the lipid-deposited surface in the aorta. The normalizing activity of serum cholesterol level in cholesterolemic rats was accelerated by Bifidobacteria. The normalizing activity of B. breve K-111 on serum cholesterol level was superior to that of B. breve K-110. These results suggest that Bifidobacteria in the human intestine playa role in the prophylactics of arteriosclerosis.