Atherosclerosis is a chronic immuno-inflammatory disease. Recent evidence has suggested an association between Chlamydia pneumoniae infection, human heat shock protein (HSP) 60 antibody and the pathogenesis and severity of coronary atherosclerosis.High degree of sequence homology between microbial and mammalian HSP60, due to evolutionary conservation, carries a risk of misdirected autoimmunity against HSPs expressed on endothelial cells that express HSPs as a consequence of different forms of stress. This study included 85 individuals and aimed at measuring the serum antibodies to C. pneumoniae and human HSP60 in young patients with severe coronary artery disease to evaluate their possible role in coronary atherosclerosis.