The lung produces many vasoactive substances originating from its vascular endothelium and plays an important part in various pathose. The present study was carried out to clarify pulmonary atherosclerosis and pulmonary arterial pressure, and to elucidate a part of the pulmonary pathosis in cholesterol-fed rabbits. Atherosclerosis was induced by feeding the animals a cholesterol-rich diet. When the rabbits were fed the cholesterol-enriched diets for 15 weeks, the grade of the atherosclerosis was severer than in 8W-feeding rabbits. The lesions of 8W-feeding rabbits were mainly composed of foam cells and fibrous components, whereas in 15W-feeding rabbits, the aggregation of foam cells beneath the endothelium of the vessel was infiltrating the media and severe stenose of the lumen was observed. In the entire pulmonary arterial system, the severe obstructive vascular lesions were localized and not diffused. The pulmonary arterial pressures of the rabbits increased slightly with time and the mean pressures were 11.3+/-0.9 (control group), 11.8+/-1.0 (8W group) and 13.7+/-1.5 mmHg (15W group) respectively. A significant difference existed in the mean pressure between the control group and 15W-feeding group, but there were no significant differences in the systolic and diastolic pressures among the three groups. In conclusion, we could induce pulmonary atherosclerosis in rabbits by feeding them a hyper-cholesterol diet but not overt pulmonary hypertension.