There is mounting evidence to suggest that Chlamydia pneumoniae might play a role in atherosclerosis. Serological studies and detection of the microorganism in atheromatous lesions were the first indications of an association between C. pneumoniae and the disease. Studies suggest that anti-chlamydial chemotherapy has a favorable effect on cardiovascular disease in humans. Moreover, infection of animals with C. pneumoniae induces inflammatory changes in the aorta that are suggestive of atherosclerosis and accelerates the progression of existing atherosclerotic lesions. If the pathogenic role of C. pneumoniae in atherosclerosis is defined more conclusively by future studies, the development of preventive or therapeutic measures against infection might provide an effective strategy to reduce the risk of atherosclerosis.