Mononuclear leukocyte–mediated inflammation is a central feature of atherosclerosis. Using measures that diminish lesion monocyte recruitment and macrophage-mediated inflammation, investigators have shown these specific events to be essential to the development and progression of atherosclerotic lesions. Lesion T lymphocytes have an activated phenotype and colocalize with lesion macrophages, particularly in early disease. However, the role of lesion T lymphocytes in atherogenesis is not as well understood as the role of macrophages.