Chlamydia pneumoniae is a ubiquitous pathogen that causes acute respiratory disease. The spectrum of C. pneumoniae infection has been extended to atherosclerosis and its clinical manifestations. Seroepidemiologic studies have associated C. pneumoniae antibody with coronary artery disease, myocardial infarction, carotid artery disease, and cerebrovascular disease. The association of C. pneumoniae with atherosclerosis is corroborated by the presence of the organism in atherosclerotic lesions throughout the arterial tree and the near absence of the organism in healthy arterial tissue. C. pneumoniae has also been isolated from coronary and carotid atheromatous plaques. To determine whether chronic infection plays a role in initiation or progression of disease, intervention studies in humans have been initiated, and animal models of C. pneumoniae infection have been developed. This review summarizes the evidence for the association and potential role of C. pneumoniae in cardiovascular disease.