Tetralogy of Fallot (ToF) is a congenital heart defect with four major features including right ventricular outflow tract obstruction. About 25 children are born with this condition in Denmark every year. Corrective surgery is usually performed within the first year. In 50 % of patients, enlargement with a patch is necessary to achieve relief of the outflow tract obstruction. This however results in severe pulmonary regurgitation, which eventually leads to volume overload, right ventricular dysfunction and arrhythmia. To avoid these late complications, pulmonary valve replacement with a prosthesis if performed when patients meet the current guideline criteria. Most patients meet the guideline criteria for revalving when they are between 20 and 30 years of age. The current guidelines however, are based solely on retrospective studies and novel research reveals that in more than 50 % of patients who are treated according to current practice, right ventricular volumes and function as well as exercise capacity and burden of arrhythmia do not normalize or improve. 500 patients with ToF will be enrolled in a multicentre, cross-sectional study, which will yield information about the long-term outcomes after initial repair of ToF, as well as suggestions about the optimal timing for re-valving. Among patients included in the cross-sectional study, 120 patients with free pulmonary regurgitation, will be randomized evenly for early or later re-valving with at least 10-years of follow-up, for evaluation of long-term efficacy and safety of early re-valving.