Over the past few years a remarkably rapid evolution in the professional level of neonatology and in the survival of immature infants has been witnessed. Persisting ductus arteriosus is common in this population and is associated with impaired longterm outcome. Many uncertainties exist concerning indication, approach, best time, and side effects of necessary measurements and interventions to avoid later neurodevelopmental handicaps of the survivors. Experts in neonatology and pediatric cardiology give their opinion in this book. We are sure it will help to define the level of evidence and to develop standards of intervention for persisting ductus arteriosus in Europe. Adequate dealing with the ductus will become a challenge for every perinatal center.