Background: High-sensitivity C-reactive protein (hs-CRP) elevation is a known contributor to the inflammatory response. This study was designed to assess whether the inflammatory state influences the recurrence of atrial fibrillation (AF) after treatment of paroxysmal AF by pulmonary vein isolation (PVI). Methods and Results: Twenty three patients who were referred to undergo PVI for drug refractory paroxysmal AF (mean duration: 70.1 ± 69.2 months) were included in the study. Body weight (BW), serum hs-CRP, brain natriuretic peptide (BNP), interleukin-6 (IL-6), carboxyl-terminal telopeptide of collagen I (ICTP), left atrial diameter (LAD), and left ventricular ejection fraction (LVEF) were measured before cardioversion. PVI was successful in all patients, but the AF recurred in 7 patients (30%) during the 2-24 month follow-up period. There were no significant differences in age, AF duration, LVEF, or baseline BNP, IL-6, ICTP levels between patients with recurrent AF and those without. However, baseline hs-CRP was significantly higher in the patients with recurrent AF than in those without (1,256 ± 940 vs. 745 ± 841 ng/ml, respectively, P = 0.02). BW and LAD tended to be greater in patients with recurrent AF than in those without (BW: 73.1 ± 13.8 vs. 62.3 ± 12.1 kg, P = 0.06; LAD: 41.0 ± 8.2 mm vs. 34.9 ± 5.9 mm, P = 0.08). Conclusion: The inflammatory state may contribute to the pathogenesis of paroxysmal AF and may be useful for predicting the recurrence of AF after PVI.