Objective. To investigate whether Chlamydia pneumoniae ( Cpn) seropositivity in patients with suspected coronary artery disease ( CAD) ( n = 81) is associated with increases in markers of inflammation, the severity of coronary atherosclerosis, and traditional risk factors for cardiovascular events. Material and methods. The severity of coronary atherosclerosis was ranked by Gensini score. Inflammation and endothelial dysfunction were evaluated using white blood cell counts and levels of high- sensitivity C- reactive protein ( hs- CRP), ferritin, tumour necrosis factor-alpha ( TNF-alpha), interleukins 1 beta and 6 ( IL- 1 beta, IL- 6), soluble intercellular adhesion molecule- 1 (sICAM-1), E-selectin and oxidized LDL ( oxLDL), and these were compared between Cpn- seropositive and seronegative individuals. Results. IgA and IgG Cpn seropositivity were significantly associated with the presence of CAD ( p = 0.005) and were independent predictive factors for the severity of coronary atherosclerosis ( p = 0.005). Elevated levels of IL- 6 ( p = 0.027) and triglyceride ( p50.038) and low levels of high- density lipoprotein cholesterol ( HDL- C) ( p = 0.038) were significantly predicted by Cpn IgA and IgG seropositivity. Conclusions. Seropositivity for Cpn is a risk factor for patients with significant angiographically documented coronary stenosis. Additionally, Cpn seropositivity was significantly associated with dyslipidemia and elevated IL-6, known risk factors for CAD. These observations indicate that Cpn infection may be one entry point to the causal or contributory pathways that lead to atherosclerosis and its clinical manifestations.