The prevalence of PAH associated with congenital systemic-to-pulmonary shunts in Western countries has been estimated to range between 1.6 and 12.5 cases per million adults, with 25-50% of this population affected by Eisenmenger's syndrome. The rarity of this syndrome, combined with its complex pathophysiology, account for the insufficient understanding of the principles underlying its proper treatment.Recent decades have seen developments in pulmonary hypertension pathophysiology which have led to the introduction of new groups of drugs: prostacycline analogs (Epoprostenol, Treprostinil, Beraprost, Illoprost), phosphodiesterase inhibitors (Sildenafil, Tadalafil), endothelin receptor antagonists (Bosentan, Sitaxantan, Ambrisentan) and nitric oxide. These drugs should be administered to patients in III-IV NYHA class. Despite successful early results, the therapeutic effect on patients with Eisenmenger syndrome has not been conclusively established The treatment strategy for patients with PAH associated with congenital systemic-to-pulmonary shunts and, in particular, those with Eisenmenger's syndrome is based mainly on clinical experience rather than being evidence based. Although Eisenmenger's syndrome is uncurable disease, the survival rate is relatively higher than primary PAH, and the patients with Eisenmenger's syndrome are relatively younger group. So the improvement of exercise tolerance and quality of life is very important. Several randomized controlled trial reported favourable short- and long-term outcomes of treatment with the orally active dual endothelin receptor antagonist bosentan in patients with Eisenmenger's syndrome. However, there was scare data of outcomes of treatment with the inhaled iloprost in patients with Eisenmenger's syndrome. In Korea, most of patients with Eisenmenger's syndrome are treated with conservative therapy instead of administration of PAH-specific drug, because of lack of clinical experience. Moreover, oral agent such as bosentan, sidenafil is preferred than iloprost becase of more evidence and convenience. Our therapeutic efforts should be directed mainly towards preventing complications. As a rule, we should avoid agents with no established therapeutic efficacy and try to alleviate symptoms without any additional risk, so as not to disrupt the existing clinical balance.