Twenty nine patients aged 15-35 years (mean 23) with tricuspid atresia and normally related great arteries were studied; 20 are alive. Ten patients who had had a Fontan operation (group 1) were compared with 10 patients with palliative shunts (9) or no surgery (1) (group 2). Patients were graded according to their ability to lead a normal life (ability index). Patients in group 1 tended to have a better ability index, a greater exercise capacity, and fewer social and extracardiac problems than those in group 2. The mean left ventricular ejection fraction measured by radionuclide angiography was the same in both groups. Arrhythmias were equally common in both groups; they appear to be age related and they occur independently of left ventricular function.