Background: Inflammation is an integral component of the atherosclerotic process, influencing both initiation and progression. Inflammatory processes within the atherosclerotic plaque have been associated with focal weakening and destabilization of the fibrous cap, thus triggering plaque rupture and thrombosis leading to acute coronary syndromes. Serum CRP level is a strong independent predictor of risk for future Myocardial infarction, Stroke, Peripheral arterial disease, and vascular death. Elevated hsCRP levels also may increase the thrombogenicity of the atherosclerotic plaque. Elevation of hsCRP is associated with an increased risk for cardiac events among the healthy population , patients with stable coronary artery disease (CAD) or acute coronary syndrome (ACS) ,and those who undergo percutaneous coronary interventions (PCIs The purpose of this study was to investigate whether mechanical rupture of an atherosclerotic coronary plaque during elective stent implantation in patients with stable coronary artery disease will cause a significant increase in serum levels of CRP. Methods and Results: We measured serum CRP levels in 40 patients. Group 1 consisted of 10 patients with stable coronary disease, before and after elective coronary stent implantation. We compared the results in these patients to those of patients in 2 control groups: Group 2 consisted of 10 patients with unstable angina who were undergoing coronary stent implantation, and Group 3 included 10 patients with stable or unstable CAD who were undergoing diagnostic coronary angiography only without PCI. Peripheral blood samples for CRP level testing were withdrawn before and after PCI or angiography at the completion of the procedure, and 6, 20, 48 hours thereafter, then follow up after 6 weeks. Group 4 consisted of 10 normal persons, no evidence of coronary artery disease. A baseline serum hsCRP levels in Group 1 patients with stable coronary artery disease was higher than the upper limit of the normal value. All patients with stable coronary artery disease (Group 1) had a significant and uniform increase in serum hsCRP levels after elective stent deployment in comparable to patients with stable angina who underwent only diagnostic coronary catheterization without PCI (Group 3 ) but it became significant after 48 hour of stent implantation (P=0.008).When stents implanted in unstable plaques in group 2 patients with unstable angina in whom the baseline hsCRP level was already elevated (Group 2), a further increase in hsCRP was observed after PCI but this was not significant, in comparable to patients in Group 3 . All measurements in the thirty patients of our study returned back to the baseline levels after 6 weeks of coronary angiography, with or without PCI. In this study no significant correlation between baseline of hsCRP and coronary heart disease risk factors, except hypertension was find. Conclusions: Mechanical disruption of an atherosclerotic coronary plaque during elective coronary stent implantation in patients with stable CAD causes a systemic inflammatory response expressed by marked elevation in CRP concentration.