Phytosterols are plant sterols with a chemical structure similar to cholesterol. It has anti-cholesterol, anti-cancer and anti-oxidant properties which are probably mediated by suppression of lipid peroxidation. However, there are limited studies on the effects of phytosterols on lipid peroxidation. The aim of this study is to determine the effects of phytosterols on plasma and tissue malondialdehyde (MDA) of rats exposed to carbon tetrachloride. The rats were divided into four groups of normal control (NC), carbon tetrachloride (CCl4), phytosterol (P) and phytosterol+carbon tetrachloride (P+CCl4). The P and P+CCl4 groups were pretreated with subcutaneous phytosterol at 140 mg/kg once weekly for 5 weeks while the NC and CCl4 groups only received olive oil (vehicle). A single oral dose of carbon tetrachloride was then given to rats in the CCl4 and P+CCl4 groups to induce lipid peroxidation. After 24 hours, all the rats were sacrificed and the plasma and tissue MDA were measured. Our results showed carbon tetrachloride had caused significant elevations of the plasma and hepatic MDA of the CCl4 group compared to the NC group. Phytosterol pretreatment (P+CCl4 INTRODUCTION Phytosterols or plant sterols are a group of steroid alcohols, phytochemicals naturally occuring in plants. They have a chemical structure which is similar to cholesterol (Weihrauch & Gardner 1978) and exist in several forms in plants (Law 2000; Katan et al. 2003; Abumweis et al. 2007) including β-sitosterol, campesterol, stigmasterol and cycloartenol (Ostlund 2002). Phytosterols are natural compo-nents found in the human diet. It made up 0.1 to 0.5% w/w of vegetable oils or margerine (Kochlar 1983) and are also found in corn, wheat and rice. Phytosterol intake varies according to the type of diet taken. Europeans consume about 200-300 mg/day of phytosterol (Morton et al. 1995) while the vegetarian Japanese have a higher intake of phytosterol (Nair et al. 1984). group) were able to prevent the MDA elevations. Phytosterols treatments in normal rats (P group) were found to reduce the hepatic MDA level. The conclusion of this study was that phytosterols are effective suppressor of plasma and hepatic lipid peroxidation. They have potential as supplements to further reduce lipid peroxidation in healthy individuals.