The Fontan operation, which places the systemic and pulmonary circulations in series and is driven by a single ventricular chamber, is the treatment of choice for patients born with one ventricle. Its introduction 35 years ago was the result of a flurry of experimental and clinical research that had started in the 1940s. A large number of children have benefited and continue to benefit from the Fontan operation, but there is a genuine concern that, despite the refinement of the surgical procedures in the past 20 years, continuing attrition might be inevitable. This adverse effect can lead to a decline in functional capacity, and premature late death.