To investigate the electrophysiologic characteristics of f-wave amplitude and to evaluate its role in development and persistence of chronic atrial fibrillation (AF) associated with rheumatic heart disease (RHD). Methods: Epicardial mapping was performed in 44 patients with chronic AF of RHD who underwent heart valve surgery. Ten patients with supraventricular tachycardia served as the control group. Results:The f-wave amplitude of left atrium (LA) and middle and low LA posterior regions were significantly lower than those of the control group. The f-wave amplitudes of the upper, middle and low sections in LA posterior region were significantly lower than those in right atrium (RA) (P<0.05). The f-wave amplitudes were compared before and after electrocardioversion in 14 patients with chronic AF. The mean atrial electrogram amplitude during sinus rhythm was significantly higher than that during AF (P<0.01).The f-wave amplitude in left appendage was higher than that in LA posterior region (the upper,middle and the lower part),P<0.05.The f-wave amplitude in the upper section of LA was significantly higher than that in the middle section. The f-wave amplitude in AF group was not correlated to the diameter or volume of both atria. Conclusion: There are amplitudes differences between the upper, middle and lower LA,suggesting that the middle and lower sections of LA posterior wall may be the region producing anisotropy and reentrant circle.