We determined the effect of inflammation on progression of atrial fibrillation (AF). Methods: Sterile pericarditis was created in 12 dogs. Before and 2 days after operation, the C-reactive protein (CRP) level, duration of induced AF, atrial effective refractory period (AERP) of the right atrial appendage, and intra-atrial conduction time were determined. Results: On the 2nd postoperative day, sustained AF (> 200 sec, mean; 540+/-351 sec) was induced in 7 dogs (group A), and non-sustained AF (less than or equal to 200 sec, mean; 82+/-84 sec) was induced in 5 dogs (group B). Group A had a higher CRP (11.8+/-1.3 vs. 7.2+/-0.6 mg/dL, p<0.001), a shorter AERP (122+/-4 vs. 139+/-13 ms, p<0.05), and a longer intra-atrial conduction time (56+/-7 vs. 46+/-5 ms, p<0.05) than group B. Conclusion: In this model, elevated CRP was associated with sustained AF, suggesting that electrophysiological changes resulting from inflammation perpetuate AF.