Atherosclerosis is a disease state where artery walls thicken as a result of a buildup of fatty materials. At Charles River, plaque formation in ApoE-/- and LDLR-/- mice is used to assess anti-atherosclerotic agents in vivo. We have vast experience with these models, removing the aorta or brachiocephalic sinus and performing either cross-section or en face staining to augment the lumen, plaque formation and macrophage infiltration. Differences between control and treatment groups are compared to assess efficacy.