Background: Concentration of cholesterol and other lipids in human diet has been considered as an issue of public health. In the present study the Effects of Peganum harmala (P. harmala) on lipid metabolism were investigated in a 28-days feeding trial. Methods: Total of 64 rats (200±15) were divided into six groups: (G1) control, G2) control plus 100mg/kg, G3) control plus 200mg/kg, G4) control plus 400mg/kg. , G5) 1%cholesterol, G6) 1% cholesterol plus 100mg/kg, G7) 1% cholesterol plus 200mg/kg, G8) 1% cholesterol plus 400mg/kg, In experiment 2, diets G5, G6, G7 and G8a diet of 1% cholesterol were fed stock diet for 4-week pre experimental period . The blood and liver tissue samples for serum lipid profile were collected and HMG COA reductase activities determined. Results: P. harmala decreased plasma cholesterol in cholesterol fed rats (100,200,400) mg/kg of the Extract, but decreased plasma triglycerides only in 200,400 mg/kg of the diet group. Peganum harmala supplementation decreased very low density lipoprotein cholesterol and increased * Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . HMG COA reductase activities: the P. harmala supplementation further decreased these enzyme activities. P. harmala at the 100 mg/kg dose was similarly effective on lipid metabolism but differences was not significantly, but in 400 mg/kg doses increased these enzyme activities was significantly (P>0.05). Conclusions: It is concluded that methanolic extract of P. harmala could be effectively used in rat to optimize serum lipid profile. These results demonstrate that P. harmala increases the effect of excretion cholesterol and not through HMG COA reductase activities inhibition.