Epidemiological studies indicate that respiratory tract and dental infections increase the risk of atherosclerotic cardiovascular disease. Several microorganisms have been claimed as clinically important, especially Chlamydia pneumoniae (Cp) and cytomegalovirus (CMV), Cp is frequently isolated from atherosclerotic plaques, and treatment with macrolide antibiotics may have a beneficial effect on the course of ischaemic heart disease. CMV seems to play a role in the development of coronary stenosis following coronary bypass surgery and heart transplantation. Likewise, inflammatory markers are associated with atherosclerotic cardiovascular disease. The pathogenetic role of microorganisms may be ascribed to the inflammatory response, which is elicited during infection. There is an urgent need for more documentation of the role of microorganisms in cardiovascular disease, and of the possible clinical effect of antibiotic treatment.