OBJECTIVES: Describe demographics, clinical characteristics and treatment patterns (i.e., discontinuation, switching, or augmentation) of patients with pulmonary arterial hypertension (PAH) initiating prostacyclin (PGI2) therapy. METHODS: Using Truven® Commercial and Medicare Databases (2010–2014), two non-mutually exclusive cohorts were constituted.  The first consisted of initiators of parenteral PGI2 (P-PGI2); the second, non-parenteral PGI2 (NP-PGI2).  All patients were required to have evidence of PAH (i.e., ≥1 claims with a PAH diagnosis or ≥1 pharmacy claims for PAH-specific medications). Demographics and clinical characteristics were assessed during the three months prior to PGI2 initiation. Treatment patterns were assessed until switch/discontinuation, or end of follow-up. RESULTS: Of the 12,306 PAH patients identified during the study period, 1,569 (12.7%) were new initiators of PGI2 (755 [6.1%] for P-PGI2 and 1,003 [8.2%] for NP-PGI2).  Approximately 70% of each cohort was female.  P-PGI2 patients were nominally younger than NP-PGI2 patients (54.2 vs. 59.4 years), yet, had more comorbidities, hospitalizations, emergency room visits and mean (standard deviation [SD]) PAH-related medical costs than NP-PGI2 patients ($46,038 [$72,208] vs. $28,210 [$58,386]) during the three months before PGI2 initiation. P-PGI2 patients had less other PAH medication use than NP-PGI2 patients prior to PGI2 initiation (43% vs. 67%). Twenty-seven percent and 19% of P-PGI2 and NP-PGI2 patients, respectively, discontinued initial PGI2; mean (SD) weeks to discontinuation was 22 (35) and 20 (23). Only 7% of P-PGI2 and 11% of NP-PGI2 patients switched; mean (SD) weeks to switch was approximately 8 (12.5) in both groups. Augmentation with another PAH medication occurred among 36% and 50% of P-PGI2 and NP-PGI2 patients, respectively; mean (SD) weeks to augmentation were 7 (15) and 3 (8).  CONCLUSIONS: Use of other PAH therapies prior to PGI2 is common, particularly among NP-PGI2.  Our findings suggest that parenteral PGI2 may be reserved for more severe PAH patients.