The relationship between pulmonary arterial hypertension-specific drug therapy (PAH-SDT) and mortality in Eisenmenger syndrome (ES) is controversial. To investigate outcomes in patients with ES, and their relationship with PAH-SDT. Retrospective, observational, nationwide, multicentre cohort study. We included 340patients with ES: genetic syndrome (n=119; 35.3%); pretricuspid defect (n=75; 22.1%). Overall, 276 (81.2%) patients received PAH-SDT: monotherapy (endothelin receptor antagonist [ERA] or phosphodiesterase5 inhibitor [PDE5I]) 46.7%; dual therapy (ERA+PDE5I) 40.9%; triple therapy (ERA+PDE5I+prostanoid) 9.1%. Median PAH-SDT duration was 5.5years [3.0-9.1years]. Events (death, lung or heart-lung transplantation) occurred in 95 (27.9%) patients at a median age of 40.5years [29.4-47.6]. The cumulative occurrence of events was 16.7% [95% confidence interval 12.8-21.6%] and 46.4% [95% confidence interval 38.2-55.4%] at age 40 and 60years, respectively. With age at evaluation or time since PAH diagnosis as time scales, cumulative occurrence of events was lower in patients taking one or two PAH-SDTs (P=0.0001 and P=0.004, respectively), with the largest differences in the post-tricuspid defect subgroup (P<0.001 and P<0.02, respectively) versus patients without PAH-SDT. By multivariable Cox analysis, with time since PAH diagnosis as time scale, New York Heart Association/World Health Organization functional classIII/IV, lower peripheral arterial oxygen saturation and pretricuspid defect were associated with a higher risk of events (P=0.002, P=0.01 and P=0.04, respectively), and one or two PAH-SDTs with a lower risk of events (P=0.009). Outcomes are poor in ES, but seem better with PAH-SDT. ES with pretricuspid defects has worse outcomes despite the delayed disease onset.