The vast majority of patients who survive surgery for repair of tetralogy of Fallot, atrial or ventricular septal defect, valvular pulmonary stenosis, or (to a lesser extent) coarctation of the aorta subsequently experience symptom-free productive lives. Nevertheless, a minority of patients with these congenital cardiac malformations may experience increased functional impairment or other complications, including sudden death later in life, despite an apparently satisfactory operation. The identification of those patients who are at risk of developing long-term postoperative problems represents a significant challenge in the management of patients with congenital heart disease. This appears to be particularly true in patients with coarctation of the aorta and in patients with tetralogy of Fallot. In patients with coarctation of the aorta, longevity is impaired, and the incidence of long-term postoperative cardiovascular abnormalities (eg, residual systemic hypertension) is high, despite adequate repair of the coarctation. This is particularly true when surgery is performed relatively late in life or when associated aortic or mitral valvular disease is present. It is also apparent that a small percentage of patients with surgically repaired tetralogy of Fallot will subsequently experience late onset of complete heart block or sudden death. Although the evidence is not yet conclusive, patients who are at increased risk appear to be those who show postoperative bifascicular block, transient complete heart block, or ventricular arrhythmias. These points emphasize the importance of early diagnosis and surgical correction, as well as long-term (if not life-long) postoperative follow-up of patients with certain congenital cardiac malformations, especially those with coarctation of the aorta or tetralogy of Fallot.