This study was performed to investigate the changes of the serological parameters of the rats fed a high fat and high cholesterol diets with or without quercetin supplement for five weeks. Thirty Sprague-Dawley male rats ($152.1{pm}17.0;g$ of body weight) were randomly divided into three groups with 10 rats in each group. Rats in the control(C) group were fed the high fat and high cholesterol diet containing 15% lard, 2% cholesterol and 0.5% sodium cholate (w/w). Rats in two treatment groups were fed the same diet supplemented with 0.25% quercetin (Q-0.25) or 0.5% quercetin (Q-0.5) on the weight to weight basis, respectively. The final body weight, gain of body weight, the amount of feed intake and the feed efficiency of rats in between control and treatment groups were not significantly different. Serum glucose, total protein, albumin, globulin and albumin/globulin (A/G) ratio of rats showed no significant differences between control and treatment groups. Serum total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C) and atherogenic index(AI) of rats in both Q-0.25 and Q-0.5 groups were significantly lower than in C group (p < 0.05). However serum high density lipoprotein-cholesterol (HDL-C) was significantly higher in both Q-0.25 and Q-0.5 groups than in C group (p < 0.05). The levels of triglyceride in sera of rats showed no significant differences between control and treatment groups. The values of AST and ALT in sera of rats showed no significant differences between control and treatment groups. Therefore the supplementation of quercetin to high fat and high cholesterol diet in rats was effective in reducing the levels of serum lipids to cause cardiovascular diseases and in elevating the level of HDL-C to protect cardiovascular diseases.