Atherosclerosis is characterized by oxidative damage which affects lipoproteins, the walls of blood vessels and subcellular membranes. This study evaluates the antioxidant capacity of a Curcuma longa extract on the lipid peroxidation of liver mitochondria and microsome membranes in atherosclerotic rabbits. Male rabbits fed a 3% (w/w) lard and 1.3% (w/w) cholesterol diet were randomly assigned to three groups. Two groups were treated with different dosages of a turmeric extract (A and B) and the third group (control) with a curcumin-free solution. Basal and in vitro 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced hydroperoxide and TBARS productions in liver mitochondria and microsomes were analyzed. Group A had the lowest concentration of mitochondrial hydroperoxides. In microsomes, the basal hydroperoxide levels were similar in all groups but, after the induction of oxidation, group C registered the highest value; TBARS production followed the same trend in mitochondria. These findings suggest that active compounds in curcuma extract may be protective in preventing lipoperoxidation of subcellular membranes in a dosage-dependent manner.