Background: Originally reported to occur predominantly in younger women, idiopathic pulmonary arterial hypertension (IPAH) is increasingly diagnosed in elderly patients. We aimed to describe the characteristics of such patients and their survival under clinical practice conditions. Methods: Prospective registry in 28 centers in 6 European countries. Demographics, clinical characteristics, hemodynamics, treatment patterns and outcomes of younger (18-65 years) and elderly (>65 years) patients with newly diagnosed IPAH (incident cases only) were compared. Results: A total of 587 patients were eligible for analysis. The median (interquartile, [IQR]) age at diagnosis was 71 (16) years. Younger patients (n=209; median age, 54 [16] years) showed a female-to-male ratio of 2.3:1 whereas the gender ratio in elderly patients (n=378; median age, 75 [8] years) was almost even (1.2:1). Combinations of PAH drugs werewidely used in both populations, albeit less frequently in older patients. Elderly patients were less likely to reach current treatment targets (6 min walking distance>400 m, functional class I or II). The survival rates 1, 2, and 3 years after the diagnosis of IPAH were lower in elderly patients, even when adjusted for age- and gender-matched survival tables of the general population (p= 0.006 by log-rank analysis). Conclusions: In countries with an aging population, IPAH is now frequently diagnosed in elderly patients. Compared to younger patients, elderly patients present with a balanced gender ratio and different clinical features, respond less well to medical therapy and have a higher age-adjusted mortality. Further characterization of these patients is required. Clinical trials registration: NCT01347216.