Although the Maze procedure has proven to be very effective in the treatment of atrial fibrillation, some authors have chosen to delete some of the important steps of the technique. Both our experimental and clinical experiences with the Maze procedure indicate that 1 of the most important principles is to interrupt conduction across the posterior-inferior portion of the left atrium. This is accomplished by creating a transmural lesion in the myocardium and then creating a circumferential lesion at the same site in the coronary sinus. We have used surgical incisions in the atrium and a cryolesion in the coronary sinus to block conduction in this area. If either fails, there is a high rate of arrhythmia recurrence.