Background-Pulmonary regurgitation (PR) late after total correction for tetralogy of Fallot may lead to progressive right ventricular (RV) dilatation and an increased incidence of severe arrhythmias and sudden death. Timing of pulmonary valve replacement (PVR) is subject to discussion, because the effect of PVR on RV function in adults is unclear. In this study, MRI was used to assess the effect of PVR on RV function and PR. Clinical improvement was established by means of the NYHA classification. Methods and Results-Twenty-six adult patients were included. Cardiac MRI was performed at a median of 5.1Ϯ3.4 months before and 7.4Ϯ2.4 months after PVR. Mean preoperative PR was 46Ϯ10% (range, 25% to 64%). After PVR, 20 of 26 patients (77%) showed no residual PR, 5 patients showed mild residual PR, and 1 patient showed moderate PR. RV end-diastolic volume (RV-EDV) decreased from 305Ϯ87 to 210Ϯ62 mL (PϽ0.001), and RV end-systolic volume (RV-ESV) decreased from 181Ϯ67 to 121Ϯ58 mL (PϽ0.001). No significant change was found in RV-EF (42% versus 42%