Classic Fontan procedures, such as atriopulmonary connection or atrioventricular connection, are associated with right atrial dilatation and several late complications. Seven patients with univentricular heart who presented with exercise intolerance (n = 7), severely dilated right atrium (n = 7) with pulmonary vein compression (n = 3), atrial arrhythmias resistant to medical treatment (n = 4), cyanosis (n = 4), diffuse effusions and oedema (n = 1), and protein-losing enteropathy (n = 1), underwent conversion to total cavopulmonary connection 5.8-14.4 years after a previous atriopulmonary connection (n = 6) or atrioventricular connection (n = 1). A 14-year-old boy who, preoperatively, was in ventricular failure and a very poor state died early after conversion because of low cardiac output. All survivors had either marked or partial clinical improvement with regression of cardiomegaly, absence of pulmonary vein compression or cyanosis, and recovery of sinus rhythm. Conversion to total cavopulmonary connection appears to be effective in the treatment of late complications after classic Fontan procedures. It should be considered early in symptomatic patients, before significant ventricular dysfunction and clinical deterioration ensue.