Atherosclerotic lesion formation starts during fetal development and progresses with age after adolescence. However, atherogenesis during the juvenile period has not been studied thoroughly. In this study, we examined the atherogenic susceptibility of juvenile rabbits to cholesterol feeding. Male New Zealand White rabbits aged 8 (younger group) and 12 (older group) weeks were fed a 0.5% cholesterol-containing diet for 8 weeks, and then their aortic atherosclerotic lesion areas were evaluated. Plasma concentrations of total cholesterol, triglycerides, and phospholipids did not differ between the two groups; however, plasma concentrations of high-density lipoprotein cholesterol were 23% lower in the younger than in the older group. Atherosclerotic lesion areas were significantly larger in the younger group (32±21%). However, only moderate changes were observed in these areas in the older group (3.3±0.3%). Histological examination showed marked intimal thickening and macrophage accumulation in the aortic lesions of rabbits in the younger group. To the best of our knowledge, this is the first study to show that dietary cholesterol-induced atherogenic changes markedly occur during a short period in juvenile rabbits.