Background: Elevated inflammatory markers have been found to correlate with higher risk for cardiac events in patients with acute myocardial infarction (AMI). It has been suggested that C-reactive protein (CRP) may be involved in the initiation process of atrial fibrillation (AF). However, the role of CRP levels in the occurence of AF in patients with AMI has not been studied. This study investigated whether CRP is a risk factor for AF in patients with acute anterior MI. Methods: We prospectively evaluated 92 consecutive patients (25 women and 67 men; aged 58 +/- 11 y) with a first acute anterior wall MI. Blood samples were obtained at the time of admission to the hospital, and serum CRP levels were measured by an ultrasensitive immunonephelometry method. All patients were evaluated by echocardiography to measure the left ventricular (LV) diameter and functions. All patients were monitored continuously for the detection of AF in the coronary care unit. Results: Atrial fibrillation occured in 19 (20%) Of 92 patients. Univariate analysis showed that patients with AF had an advanced age (63 9,9 versus 56.7 +/- 11.7 y, p = 0.034), higher serum CRP level (2.95 +/- 2.5 versus 1.71 +/- 2.12 mg/dL, p = 0.034), larger LV end-systolic volume (74 +/- 15 versus 63 +/- 19, mL p = 0.02), higher LV ejection fraction (31.1 +/- 6.2 versus 38.4 +/- 10%, p = 0.001), and larger left atrial (LA) diameter (37.1 +/- 4.2 versus 34.7 +/- 3.3 mm, p = 0.01). In multivariate analysis, only age (odds ratio [OR]: 1.05, 95% confidence interval [Cl] 1-1.111, p = 0.036) and CRP levels (OR: 1.27, 95% Cl: 1-1.59, p = 0.039) were independent predictors of AF. Conclusion: These results suggest that CRP may be a risk factor for AF in patients with acute anterior wall MI.