According to several published studies micro-organisms may be involved in atherogenesis. An association is described between cytomegalovirus or Chlamydia pneumoniae and an increased risk of vascular events. The micro-organisms are able to infect endothelial cells and smooth muscle cells in vivo and in vitro, evoking to pathophysiological reactions of these cells which may lead to atherosclerosis, arterial thrombosis and plaque rupture. In two small secondary prevention trials, macrolide treatment proved successful in preventing second myocardial infarctions. At this moment, however, it is too early for treatment with antimicrobial agents to prevent vascular diseases in daily clinical practice.