Allium porrum L. is a herbaceous plant from the Liliaceae family and has been widely used in Persian foods as a flavor component and in Iranian traditional medicine as an anti-atherogenic remedy. The present investigation was undertaken to evaluate the antihypercholesterolemic effect of a hydroalcoholic extract of A. porrum L. bulbs. Rabbits were divided into five groups--control, hypercholesterolemic control, and three treatment groups (hypercholesterolemic diet + 250, 500, or 1,000 mg/kg of body weight of extract, respectively)--and were fed for 12 weeks. Blood samples were obtained to analyze plasma cholesterol, triglycerides, and low-density lipoprotein (LDL), very LDL, and high-density lipoprotein (HDL) cholesterol. Body weight increased in all groups throughout the treatment without significant differences among them. Plasma total cholesterol increased with respect to the control in the positive control group at the end of the treatment. Plasma total cholesterol decreased in all groups treated with A. porrum extract in a dose-dependent fashion. Changes in the distribution of cholesterol in HDL or LDL were found, and LDL cholesterol decreased significantly in all of the groups treated with A. porrum extract with respect to the hypercholesterolemic group. Thus, these findings indicate that this plant may be useful for the treatment of hypercholesterolemia.