The aim of this study was to evaluate the effects ofconsumption of different amounts of fermented milk by L.casei on serum lipid trends including total cholesterol, LDL-C, HLD-C, VLDL-C and triglyceride in the serum of rats fed 1 and 2% cholesterol enriched diet. For this purpose 49 male albino wistar rats with a body weight of 200±15 gr were randomly allocated to seven groups each containing 7 rats and adapted to new conditions during a week. Rats in the first group (control group) received commercial diet and water for 30 days, the second to fourth groups received diet enriched with 1% cholesterol and rats in the fifth to seventh groups received diet enriched with 2% cholesterol. Each rat in the fourth and seventh groups (double dose receiving treatment groups) consumed fermented milk containing 4×108 CFU bacteria per day, rats in the third and sixth groups (single dose receiving treatment groups) consumed fermented milk containing 2×108 CFU bacteria per day and in the second and fifth groups (sham group) consumed sterilized milk instead of fermented milk. According to the statistical tests, one way analysis of variance and Tukey at a level of α= 0.05, mean levels of total cholesterol and LDL-C of rats in the  double dose receiving treatment groups and single dose receiving treatment groups were significantly lower and mean level of HDL-C was significantly higher than sham group (p