Arterial inflammatory responses are thought to be a significant component of atherosclerotic disease. We describe here, using a transgenic approach, the mutual perpetuation of immune-mediated arterial inflammation and cholesterol-induced atherosclerosis. Mice expressing the bacterial transgene β-galactosidase exclusively in cardiomyocytes and in smooth muscle cells in lung arteries and the aorta (SM-LacZ), and hypercholesterolemic apolipoprotein E-deficient SM-LacZ mice (SM-LacZ/apoE^−/−) developed myocarditis and arteritis after immunization with dendritic cells presenting a β-galactosidase-derived immunogenic peptide. Hypercholesterolemia amplified acute arteritis and perpetuated chronic arterial inflammation in SM-LacZ/apoE^−/− mice, but had no major impact on acute myocarditis or the subsequent development of dilated cardiomyopathy. Conversely, arteritis significantly accelerated cholesterol-induced atherosclerosis. Taken together, these data demonstrate that the linkage of immune-mediated arteritis and hypercholesterolemia favors initiation and maintenance of atherosclerotic lesion formation. Therapeutic strategies to prevent or disrupt such self-perpetuating vicious circles may be crucial for the successful treatment of atherosclerosis.