Patients who have undergone atriopulmonary Fontan procedures are at risk for significant atrial arrhythmias and obstructive connections, which have been related to intra-atrial suture lines, atrial enlargement, and somatic growth. Twenty patients (mean age, 17.3 +/- 6.8 years) had conversion to total cavopulmonary artery connection 8.9 +/- 2.1 years after the previous Fontan procedure (for atrial arrhythmias in 19 patients and for obstructive lesions in one). Arrhythmia ablative surgery evolved over the study period from "arrhythmia circuit cryoablation" (cryoablation lesions completing lines of block) to the more standard approaches of modified right-sided Maze and Maze-Cox III procedures. Preoperative functional New York Heart Association class was IV in nine patients, III in nine, and II in two. All patients survived. Two patients had prolonged chest drainage (there was pericardial effusion in one). The average length of hospital stay was 11.3 +/- 5.4 days; chest tubes were removed on day 8.5 +/- 5.4. There were no long-term deaths (mean follow-up period, 20.3 +/- 14.9 months; range, 2 months to 4 years). Late postoperative arrhythmias occurred in two patients who are receiving long-term antiarrhythmic medications. All patients have improved to New York Heart Association class I or II. Total cavopulmonary artery Fontan conversion in association with modified right-sided Maze or Maze-Cox III procedures and pacemaker placement can be accomplished with low morbidity and mortality, and results in functional class improvement and control of life-threatening arrhythmias. Copyright 1999 by W.B. Saunders Company