There is an increasing body of evidence that links Chlamydia pneumoniae infections to atherosclerosis and the clinical complications of unstable angina, myocardial infarction and stroke. Several epidemiologic reports indicate an association between the presence and titer of Chlamydia pneumoniae antibodies and atherosclerosis and its complications. Other studies show the presence of Chlamydia pneumoniae, chlamydial antigens or nucleic acid in atherosclerotic plaques. Moreover, experimental studies present mechanisms by which Chlamydia pneumoniae may play a role in the induction of atherosclerosis and its complications. Finally, many studies have evaluated the effect of antibiotic treatment on cardiovascular events in humans. This article reviews all the aspects that link Chlamydia pneumoniae to atherosclerosis and its clinical manifestations.