Whole oats have cholesterol-lowering effects, but the mechanisms behind this and other possible effects on the vascular bed are unknown. Clarification of these may allow the development of food components with improved health effects. One hypothesis is that the soluble fibres in oats, beta-glucans, reduce intestinal uptake of dietary cholesterol and reabsorption of bile acids. Other interesting oat components are avenanthramides, which in vitro have been shown to increase NO production and decrease monocyte attachment to endothelial cells. Several genetically modified mouse models presenting hyperlipidemia and atherosclerosis are available, but no single model reproduces human atherosclerosis in all aspects. In initial studies we have used a mouse strain, C57BL/6, with an increased tendency for atherosclerosis but no overt defect in lipoprotein metabolism. The mice were fed an atherogenic diet supplemented with either oat bran (40%) or control fibres (cellulose). Total plasma cholesterol increased rapidly in both groups, but after one week it was significantly lower in the mice fed oat bran (130 mg/dL vs. 150 mg/dL, n = 10, p < 0,05). After four weeks on the diet, there were no significant difference in plasma cholesterol (164 mg/dL vs 153 mg/dL, n = 10). Thus oat bran seems to delay the increase in plasma cholesterol in C57BL/6 mice on atherogenic diet but is not able to cause a sustained decrease. There were no differences in the lipoprotein composition or triglyceride levels between the groups. Genetically modified mice, where clearance of lipoprotein particles is inhibited, might be needed to evaluate the effects of oats on cholesterol uptake.