Recent studies have illustrated that in addition to the well known risk factors, such as lipoproteins, smoking, hypertension, there are others that cause atherosclerosis and myocardial infarction. Our knowledge of atherosclerotic lesions has increased. We now know that atherosclerotic changes are due to inflammatory cell infiltration as well as to increases in migration of vascular smooth muscle cells. Endothelial cells play a major role in the pathology of vascular changes. In recent years a new risk factor for coronary artery disease has been discovered: chlamydia pneumonial infections. Herpes class viruses have also been associated with pathology of atherosclerotic lesions. Studies show that dental status and bacterial infections are also related to the risk of myocardial infarction. This review discusses the possible mechanisms of infection and inflammation and whether they are major or modifying risk factors for atherosclerosis and myocardial infarction.