Cholesterol oxidation products (COPs) have been associated with the genesis of chronic degenerative diseases, such as atherosclerosis. The purpose of this work was to study the histological changes by toxic effects of dietary COPs in liver and kidney. Five-week-old male Wistar albino rats were randomly divided into three groups of 10 rats each. Standard rat chow was supplemented with either 1% (w/w) pure cholesterol or 1% oxidized cholesterol and fed to the rats for 8 weeks. Control animals were fed standard rat chow. At the end of the treatment period, the serum lipid profile was determined. The aorta, liver and kidneys were excised immediately, frozen with liquid nitrogen, and held at -70 degrees C. The histological study was carried out using conventional hematoxylin-eosin staining, and histochemical red oil 'O' was applied. COPs were analyzed by gas chromatography. Intake of dietary COPs altered biochemical parameters involved in lipid metabolism associated with atherogenesis in rats: total cholesterol, triacylglycerols and low density lipoproteins in serum. COPs detected in the liver and kidneys modified the organ original structure, caused an inflammatory process and promoted atherogenesis and atrophy of the tissue.