Rabbits were fed with two kinds of atherogenic diet, one containing 0.5% cholesterol and 3% soybean oil and the other 0.5% cholesterol and 6% peanut oil, for three months to compare the atherogenic property of the diets. The soybean oil diet seemed to be superior to the peanut oil diet for evaluation of the anti-atherogenic effect of drugs, because the former caused milder vascular lesions than the latter. Using this rabbit model for atherosclerosis, the anti-atherogenic effect of clentiazem, a new calcium antagonist, was examined. Clentiazem at an oral dose of 30 mg/kg/day significantly reduced the size of atheromatous lesion in the aortic arch and thoracic aorta, and lowered the collagen content of the aortic intima and media, although it did not decrease serum lipid levels. On the other hand, clentiazem showed no clear effect on reducing the coronary atherosclerotic lesions. These results suggest that clentiazem may inhibit the progression of diet-induced aortic atherosclerosis without normalizing the serum lipid levels.