The effect of ropy fermented milk on serum cholesterol in rats was studied. Basic diets containing slime-forming Lactococcus lactis subsp. cremoris SBT 0495, its non slime-forming variant SBT 1275, and acidified reconstituted skim milk, with 0.5% cholesterol added, were fed to F-344 rats for 7 days. Serum cholesterol level of rats fed the ropy fermented milk were the lowest among the three treatments. The serum high-density lipoprotein (HDL) cholesterol/total cholesterol ratio of rats fed ropy fermented milk was the highest. Slime materials produced by L. lactis subsp. cremoris SBT 0495 had a beneficial effect on rat cholesterol metabolism.