The theories formulated to explain atherogenesis evolved from vessel wall lipid to endothelial dysfunction with vascular wall remodelling. Chlamydia pneumoniae has been demonstrated to play an important role in the development of inflammatory and immunological process and can initiate atherogenesis. This pathogen is found in atherosclerotic plaques, which can induce complex activation of local inflammatory and immunological events and lead to the development of unstable plaque, vascular remodelling and vessel lumen constriction.