Ectopic electrical stimuli which generate atrial fibrillation are located principally in the pulmonary veins. Objective. To show that simple isolation of the pulmonary veins is enough to eliminate the atrial fibrillation, whereas mitral valve surgery. Material and Methods. From August 1998 to January 2003, fifty nine patients with mitral valve disease and atrial fibrillation were operated on. All patients underwent mitral valve surgery, simple or combined, as well as simple surgical isolation of the pulmonary veins. Mean preoperative duration of the atrial fibrillation was 3.9 ± 2.9 years. Results. Two cases (3.2%) died because of low cardiac output. Mean aortic-cross clamping and cardiopulmonary bypass times were 83 ± 26.7 minutes, and 114.6 ± 46.5 minutes, respectively.Ten patients (17%) show relapse of the atrial fibrillation into the first postoperative week. At a follow-up of 11.2 months (range, 3 to 58 months), 50 patients (86%) exhibit normal sinus rhythm. Conclusions. Isolation of the pulmonary veins can eliminate safely the chronic atrial fibrillation in the cases undergoing mitral valve surgery. This outcome emphasize the idea about the surgical management for chronic atrial fibrillation must be focused exclusively in the pulmonary veins.