Objectives. To depict the interaction between atrial fibrillation (AF) and inflammatory reaction, studies were taken to measure the activity of NF-B in myocardium, the concentration of regional inflammatory factors and the pathological process of the right atrium in patients with AF. Design. Patients with valvular disease with AF or sinus rhythm (SR) were recruited and compared. Before the extracorporal circulation, about 250 mg tissue of right atrium was collected for pathological examination. The activity of NF-B in myocardium was measured by electrophoretic mobility shift assay (EMSA), and the concentration of cardiac tissue interleukin-6 (IL-6) and tumor necrosis factor (TNF-) was determined by radioimmuoassay. Results. Patients with valvular disease with AF exhibited higher NF-B activity, higher concentration of TNF- and IL-6, severe lymphomonocyte infiltration, and more fibrosis than those patients with valvular disease with SR. There were significant positive correlations among NF-B activity and levels of TNF- and IL-6 and collagen volume fraction. Conclusions. This study proved the presence of inflammation in atrial myocardium by triggering inflammatory reaction.