A body of evidence supports an association betweenChlamydia pneumoniaeand atherosclerosis. Recent prospective, seroepidemiologic studies have refined estimations of relative risk. Advances in diagnostic testing with the polymerase chain reaction have created a potential opportunity to screen for infected individuals. New insights into the pathogenesis of infection withC. pneumoniaehave been reported, many of which are relevant to the development of atherosclerotic plaque. Clinical trials have now been initiated and should provide guidance as to the utility of antibiotics in the treatment or prevention of coronary artery disease.