SummaryEvidence suggests that inflammation plays a key role in the pathogenesis of atherosclerosis. The chronic inflammatory process can develop to an acute clinical event by the induction of plaque rupture or plaque erosion and therefore cause acute coronary syndromes.This study aimed to determine the serum levels of the circulating acute-phase reactant C-reactive protein (CRP), which is a sensitive indicator of inflammation, in patients with recurrent chest pain with positive exercise test and patients with acute myocardial infarction.This study has been carried out in Internal medicine and Cardiology departments Faculty of Medicine, Zagazig University in the period from September 2003 to September 2004.The study included 75 patients: 1) 25 patients with recurrent chest pain negative ECG and negative exercise test serving as the control. 2) 25 patients with recurrent chest pain, negative ECG and positive exercise test. 3) 25 patients presented with acute myocardial infarction.The three groups were subjected to full clinical evaluation and laboratory studies, by which exclusion was done to any patient with any condition that may elevate CRP level, and estimation of CRP levels. CRP levels were determined with a commercially available kit which is a latex reagent for quantitative estimation of CRP.CRP levels were significantly increased in patients with acute myocardial infarction and patients with stable CAD.There was significant difference of CRP levels between AMI patients and patients with stable CAD.CRP was significantly increased in patients with extensive MI more than patients with lateral, inferior or posterior M.I.There was positive correlation between CRP and CK, CK-MB in patients with acute myocardial infarction. Furthermore, CRP may be considered as a marker of the extent and severity of myocardial infarction.CRP was associated with CAD risk factors including DM, HTN and smoking. The levels of CRP was significantly increased in patients with more than one risk factor.Lastly, there is a strong association between CRP and CAD starting from early stages of atherogenesis passing through atherosclerosis and its lesions, clinical presentations of CAD whether stable CAD or its acute events.Conclusion The data of the present study showed significant increase of CRP levels, an acute phase reactant, among patients with stable CAD. CRP levels were also significantly elevated in AMI patients included in this study. CRP levels were significantly higher in patients with AMI than those with stable CAD. CRP was found to reflect the extent and severity of AMI. Furthermore, CRP is implicated in myocardial damage and increasing extent of infarction by complement activation. CRP was associated with major CAD risk factors including D.M, hypertension and smoking. CRP is a promising marker in CAD reflecting and implicating in all stages of atherosclerosis and its acute complications.