Cardioversion for atrial fibrillation (AF) is the most effective treatment for the restoration of sinus rhythm (SR). Recently, an elevated level of hs-CRP has been shown to be associated with AF burden, suggesting that inflammation increases the propensity for persistence of AF. We examined whether the level of high-sensitivity C-reactive protein (hs-CRP) was predictive of the outcome of cardioversion for AF.One hundred and six patients with a history of symptomatic AF lasting ≥1 day (age 63±14 years, mean±S.D.) underwent cardioversion. Echocardiography and hs-CRP assay were performed immediately prior to cardioversion. SR was restored in 84 patients (79%). By using selected cutoff values, multiple discriminant analysis revealed significant associations between successful cardioversion and a shorter duration of AF (AF duration≤36 days, odds ratio (OR), 0.98; 95% confidence interval (CI), 0.97–0.99), smaller left atrial diameter (left atrial diameter≤40 mm, OR 0.82, 95% CI 0.71–0.94), better-preserved left ventricular ejection fraction (left ventricular ejection fraction≥60%, OR 0.92, 95% CI 0.86–0.99), and lower hs-CRP level (hs-CRP≤0.12 mg/dL, OR 0.33, 95% CI 0.21–0.51). During a follow-up period of 140±144 days, AF recurred in 64 patients (76%). By using a cutoff value of hs-CRP≥0.06 mg/dL, Cox proportional-hazards regression model found that only hs-CRP level was an independent predictor of AF recurrence (OR 5.30, 95% CI 2.46–11.5) after adjustment for coexisting cardiovascular risks. When patients were divided by the hs-CRP level of 0.06 mg/dL, percentage of maintenance of SR below and above the cutoff was 53% and 4%, respectively (log–rank test, p<0.0001).hs-CRP level determined prior to cardioversion represents an independent predictor of both successful cardioversion for AF and the maintenance of SR after conversion.