OBJECTIVE: The aim of this study was to evaluate the effects of an oral supplementation with a Curcuma longa ethanol and aqueous extract on the susceptibility to oxidation of cellular and subcellular membranes affected in the atherosclerotic process, such as erythrocyte membranes and liver microsomes, in rabbits fed with a high-fat diet. METHODS: Twenty-four male rabbits were randomly assigned to one of two groups: group T was treated with a turmeric hydroalcoholic extract (1.66 mg/kg of body weight) dissolved in a hydroalcoholic mixture vehicle (7:2), and group C (control): received a curcuma-free hydroalcoholic solution (7:2). All rabbits had access ad libitum to 150 g/d of an experimental diet rich in cholesterol and lard to provoke an atherosclerotic process. Erythrocyte membranes and liver microsomes were isolated, and the levels of hydroperoxides and thiobarbituric acid-reactive substances were measured after oxidation induction. RESULTS. The oxidation of erythrocyte membranes in group T was significantly lower than that in group C, mainly by 30 d (P < 0.05). Levels of hydroperoxides and thiobarbituric acid-reactive substances in liver microsomes also were significantly lower in group T than in group C (P < 0.05). CONCLUSION: The results of this study indicated that oral administration of a nutritional; dose of C. longa extracts reduces the susceptibility to oxidation of erythrocyte and liver microsome membranes in vitro and may contribute to the prevention of effects caused by a diet high in fat and cholesterol in blood and liver during the development of atherosclerosis, (C) Elsevier Inc. 2003.