Chlamydia pneumoniae have been demonstrated in atherosclerotic lesions but not in normal arteries. An animal model of both C. pneumoniae and atherosclerosis is needed to investigate the role of the organism in atherosclerosis. Apolipoprotein (apo) E-deficient transgenic mice, which spontaneously develop atherosclerosis, and C57BL/6J mice, which only develop atherosclerosis on an atherogenic diet, were evaluated. Following single and multiple intranasal inoculations of apoE-deficient transgenic mice, C. pneumoniae were detected in lung, aorta, and spleen for 20 weeks after inoculation in 25%-100% of mice. In the aorta, C. pneumoniae were detected within the atherosclerotic lesion. In C57BL/6J mice on a nonatherogenic diet, C. pneumoniae were detected in the aorta only 2 weeks after a single intranasal inoculation in 8% of mice. The persistence of C. pneumoniae in atheromas suggests a tropism of C. pneumoniae to the lesion. These mouse models should be useful for studying the pathogenic role of C. pneumoniae in atherosclerosis.