Résumé : Pulmonary arterial hypertension (PAH), associated with congenital heart disease (CHD), usually results from a systemic-to-pulmonary shunt. Eisenmenger syndrome (ES) is characterised by severe irreversible PAH and reversal of a previous systemic-to-pulmonary shunt. A national registry of ES patients was initiated to optimise patient care and to provide epidemiological information regarding PAH and CHD in Belgium.