The population of patients with adult congenital heart disease is approximately 800,000 in the U.S. Those with prior cardiac surgery often consider themselves "cured," although the majority faces a lifetime of problems including arrhythmias, ventricular dysfunction, and one or more re-operations. Even patients with repaired "simple" lesions such as an atrial septal defect may not have normal survival if they are repaired in adulthood. Patients with repaired coarctation may have premature cardiovascular complications including sudden cardiac death, myocardial infarction, and stroke. They also have aortic complications such as aneurysm and dissection, which result from a diffuse arteriopathy and continued hypertension that may be caused by underlying endothelial dysfunction. In addition, bicuspid aortic valve occurs in more than one-half of the patients with coarctation, so continued surveillance for significant aortic valvular heart disease is necessary. More complex lesions also pose problems after "total correction." Patients with repaired tetralogy of Fallot often have pulmonary regurgitation, which is frequently overlooked on clinical exam and echocardiography. Pulmonary valve replacement should be performed before the development of irreversible right ventricular dysfunction and an increased risk of ventricular tachycardia or sudden cardiac death. Because they are vulnerable to deterioration of systemic ventricular function, those with congenitally corrected transposition require special vigilance, usually with concomitant atrio-ventricular valve regurgitation. Late referral is common with a deleterious effect on long-term survival. These patients need lifelong follow-up and the residua and sequelae of their complex anomalies must be understood in order to provide optimum care.