Epidemiological studies have suggested that intake of whole grains is inversely associated with coronary artery disease. The mechanisms, however, are not completely clear. We tested the hypothesis that intake of wheat bran or corn bran would (1) increase the plasma concentration of phenolic antioxidants and (2) reduce atherosclerosis in apo E-knockout mice. Apo E-knockout (E-KO) mice were fed for 18 weeks with a 0.1% cholesterol-supplemented diet in the absence of grain brans or the presence of 1.7% yellow dent corn bran or 3.3% hard red spring wheat bran. The concentration of antioxidant ferulic acid in plasma and urine was measured by HPLC to monitor the bioavailability of grain phenolics. Plasma lipoprotein profiles were determined by a combination of HPLC and online enzymatic methods. Urinary 15-isoprostane F(2t), an in vivo LDL oxidation biomarker, and atherosclerotic lesions were analyzed by ELISA and histological methods, respectively. Dietary supplementation with corn or wheat bran resulted in a 4- and 24-fold increase, respectively, in urinary excretion of ferulic acid. The urinary recovery rate of ferulic acid from the two brans in apo E-KO mice was approximately 1.9-2.9%. Dietary corn bran but not wheat bran also significantly increased the concentration of total ferulic acid in plasma. Nevertheless, the supplementation with either bran product for 18 weeks did not significantly alter the urinary excretion of 15-isoprostane F(2t), change the lipoprotein profiles, nor reduce the atherosclerotic lesion development in this animal model. The results suggest that phenolic antioxidants from the two types of bran may not be sufficient to reduce atherosclerosis in this animal model.