A simple method to quantitatively evaluate atherosclerosis in the rabbit aorta by measuring macroscopic lesion areas (%) was attempted in the present study. Ten female New Zealand white rabbits were fed on a cholesterol-rich diet (5/1000 g of food) during 4 months. Five of them were oophorectomized at the beginning and all were sacrificed at the end. Total levels of cholesterol increased from 50.7+/-14.7 mg/dl to 782.8+/-296.0. No significant differences were observed between oophorectomized and intact rabbits. At 4 months, the cholesterol-rich diet caused in both, intact and oophorectomized rabbits, atherosclerotic lesions affecting 17 and 46% of the aortic surface, respectively. This method may be more practical, easy and useful for quantitative evaluation of aortic atherosclerosis in a large number of rabbits, than histological observations of serial sections of rabbit's aortas.