This study investigates the importance of right atrial conduction features in predicting of immediate recurrence of atrial fibrillation (AF) after internal cardioversion (IC). Patients with chronic AF who were resistant to external cardioversion were studied. Twenty-four patients (16 female, 8 male mean age 58 +/- 7 years) who were successfully converted to sinus rhythm (SR) by IC, and experienced recurrence of AF within I minute of restoration of SR were enrolled in group A. Thirty-four patients, who were converted to SR by IC and in whom SR was maintained at least I minute after IC, were enrolled in group B (24 female, 10 male mean age 56 +/- 6 years) as control. There was no difference in age, left atrial diameter, use of antiarrhythmic drug, etiology and duration of AF between the groups. After successful IC, His bundle electrocardiograms via placed electrode catheters, and surface electrocardiograms were recorded for I minute. P-A interval duration, as a marker of right atrial conduction, was measured from the onset of the earliest registered surface P wave to the onset of the atrial deflection on His-bundle catheter recording. The difference between the recorded maximum P-A duration and minimum P-A duration obtained in I minute after IC was described as P-A interval absolute difference. There were no differences in the maximum P-A duration and minimum P-A duration between two groups. But, the P-A absolute difference was more pronounced in group A compared to group B (16.9 +/- 7.7 ms versus 10.3 +/- 6.4 ms, P < .001) and was significantly correlated with P wave dispersion derived from the surface electrocardiogram (r = .72, P < .001) In conclusion, variations in right atrial conduction might play an important role in predicting immediate recurrence of AF in patients converted to SR by IC.