Eisenmenger syndrome (ES) represents the most severe phenotype of pulmonary arterial hypertension (PAH) associated with congenital heart disease (CHD) and occurs in patients with large unrepaired shunts. Despite early detection of CHD and major advances in paediatric cardiac surgery, ES is still prevalent and requires a multidisciplinary approach by adult CHD experts in tertiary centres. Central cyanosis is the primary clinical manifestation leading to secondary erythrocytosis and various multiorgan complications that increase morbidity and affect quality of life. Close follow-up is needed to early diagnose and timely manage these complications. The primary goal of care is to maintain patients' fragile stability. Although the recent use of advanced PAH therapies has substantially improved functional capacity and increased life expectancy, long-term survival remains poor. Progressive heart failure, infectious diseases and sudden cardiac death comprise the main causes of death in patients with ES. Impaired exercise tolerance, decreased arterial oxygen saturation, iron deficiency, pre-tricuspid shunts, arrhythmias, increased brain natriuretic peptide, echocardiographic indices of right ventricular dysfunction and hospitalisation for heart failure predict mortality. Endothelin receptor antagonists are used as first-line treatment in symptomatic patients, while phosphodiesterase-5 inhibitors may be added. Due to the lack of evidence, current guidelines do not provide a clear therapeutic strategy regarding treatment escalation. Additional well-designed trials are required to assess the comparative efficacy of various PAH agents and the benefit of combination therapy. Finally, the development of a risk score is of utmost importance to guide clinical therapy.