Problem statement: Hyperlipidemia is well known to play a main role in the development of atherosclerosis. It is characterized by abnormally elevated cholesterol, triglyceride, low density lipoprotein cholesterol and very low density lipoprotein cholesterol levels in the blood. It has been recognized for many years that hypercholesterolemia is a major risk factor for cardiovascular diseases such as atherosclerosis, myocardial infraction, heart attacks and cerebrovascular diseases. In recent years, Coenzyme Q10 has gained considerable attention as a dietary supplement capable of influencing cellular bioenergetics and as a supplementary treatment for some chronic diseases. Approach: The present study was undertaken to evaluate whether Coenzyme Q10 supplementation would alter high cholesterol dietinduced hypercholesterolemic model in female rats. Sixty female albino rats of the Wistar strain weighing between 34.3 and 42.1 g were used. The experimental animals were divided into six groups. Rats of group 1 served as controls, fed with standard diet and had free access to water for three months. Rats of group 2 were daily supplemented with 1 mL of corn oil containing 10 mg of cholesterol/rat for two months. Animals of group 3 were daily supplemented with 1 mL of corn oil containing 10 mg of cholesterol/rat for two months and daily supplemented with 1 mg Coenzyme Q10/rat at third month. Rats of group 4 were daily supplemented with 1 mL of corn oil /rat for two months. The experimental rats of group 5 were daily supplemented with 1 mL of corn oil /rat for two months and daily supplemented with 1 mg Coenzyme Q10/rat at third month. Rats of group 6 were supplemented with 1 mg Coenzyme Q10/rat at third month. The body weight percentage changes were determined after second and third months in all experimental groups. Results: After 2 months, the maximum changes of body weight were noted in groups treated with high cholesterol diet and corn oil. After three months, the maximum percentage changes were observed in groups two and four and the minimum changes were noted in sixth group supplemented with only Coenzyme Q10 at last period. Serum triglycerides, cholesterol, High Density Lipoprotein Cholesterol (HDL-C), Low Density Lipoprotein Cholesterol (LDL-C), Very Low Density Lipoprotein Cholesterol (VLDL-C), Atehrogenic Index (AI) and HDL Cholesterol (HDL-C) ratio were assessed at the end of experimental period. Significant increases in the levels of triglycerides, cholesterol, LDL-C VLDL-C were noted in rats supplemented with high cholesterol diet, while the level of HDL-C was significantly reduced. Similar observations were noted in rats treated with high cholesterol diet plus Coenzyme Q10. Statistically, the treatment of Coenzyme Q10 in rats subjected to high cholesterol diet showed a decrease in the change levels of these parameters. Also, the Atehrogenic Index (AI) value was significantly elevated in rats supplemented with high cholesterol diet compared with control value. Administration of Coenzyme Q10 for a peri...