Background. The long-term results of the Cox-Maze III procedure (CM-III) for chronic atrial fibrillation (AF) associated with rheumatic mitral valve (MV) disease have not been reported yet. Methods. We retrospectively analyzed 127 patients who underwent the CM-III combined with a rheumatic MV procedure between 1994 and 2004. In-hospital mortalities were excluded from the study. Concomitant procedures were mitral valve replacement (MVR) (n=38), MVR and aortic valve replacement (AVR) (n=25), MV repair (n=21), MVR and tricuspid annuloplasty (TAP) (n=9), MVR and aortic valvuloplasty (AVP) (n=3), MVR and coronary artery bypass grafting (CABG) (n=2), MVR and AVR and CABG (n=2), redo-MVR (n=12), redo-MVR and TAP (n=7), redo-MVR and redo-AVR (n=7), and redo-MVR and AVP (n=1). Results. There were 4 late deaths and one follow-up loss during the period. Normal sinus rhythm was restored in 83.5% (106/127) after the CM-III. Twelve patients remained in AF and 2 patients in junctional rhythm. Permanent pacemakers were implanted in 6 patients due to sick sinus syndrome. Late recurrence of AF developed in 33 of 106 patients at a mean of 43짹27 months postoperatively, and sinus conversion restored in 25 of 33 patients by addition of an antiarrhythmic agent. Normal sinus rhythm was maintained in 77.2%(98/127) at the latest follow-up. Right atrial contractility was demonstrable in 100% (98/98) and left atrial contractility in 67.3%(66/98) of the patients in the latest follow-up echocardiography. Sinus conversion rate decreased progressively during the follow-up period (83.2%, 104/125 at 6 mo, 82.1%, 96/117 at 1 yr, 79.4%, 81/102 at 2 yr, 75.3%, 73/97 at 3 yr, 74.7%, 68/91 at 4 yr, 72.1%, 62/86 at 5 yr, 70.7%, 53/75 at 6 yr, and 69.4%, 43/62 at 7 yr postoperatively; p<0.05). Conclusions. The CM-III for chronic AF associated with rheumatic MV disease demonstrated a significantly decreased sinus conversion rate during the long-term follow-up period, which might result from aging process or degenerative changes to the atrial tissue occurring in rheumatic valvular heart disease.