Background: In the previous in vitro study, we found that simvastatin decreased the protein expression of CD36, the scavenger receptor, and calpain-1, the Ca2+-sensitive cysteine protease, in oxidized low-density lipoprotein (oxLDL)-treated macrophages. In this in vivo study, we investigated whether simvastatin downregulates the expression of CD36 and calpain-1 and inhibits the inflammation and atherosclerosis in apolipoprotein E knockout (ApoE KO) mice. Methods: Twenty male 6-week-old ApoE KO mice were divided into 2 groups: the ApoE KO group and the ApoE KO + simvastatin (ApoE KO + Sim) group. Atherosclerotic lesions were evaluated and the expressions of CD68, CD36, and calpain-1 in aorta were examined. Results: Simvastatin inhibited the atherosclerotic lesion in ApoE KO mice. In addition, simvastatin reduced the contents of oxLDL, thiobarbituric acid reactive substances, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in serum, decreased the mRNA and protein expressions of CD36 and reduced the mRNA expression of TNF-α and IL-6 in the aortas. Furthermore, simvastatin reduced the calpain activity and the protein expression of calpain-1 in the aorta. Conclusion: The results suggested that the attenuation of atherosclerotic lesions in ApoE KO mice by simvastatin might be associated with the downregulations of CD36 and calpain-1 and with inflammation.