OBJECTIVES:  Pulmonary arterial hypertension (PAH) is a chronic and progressive disease characterized by high pressure in the pulmonary arterioles, with increased pulmonary vascular resistance that can result in right heart failure and premature mortality. With several new PAH medications available since 2013, more information is needed regarding treatment patterns, persistence, and adherence. METHODS:  Patients with a diagnosis code for pulmonary hypertension and treated with an approved medication for PAH (ERAs, PDE-5is, prostacyclins, sGCs) identified by pharmacy claims between January 2010 and March 2015 were included. Patients were ≥18 years old with continuous enrollment in a large US health plan with medical and pharmacy coverage for 6 months before (with no PAH medication claim) and ≥1 year after initiating a PAH-related medication. Patients were followed until disenrollment from the plan or end of study (March 2016). Initial and subsequent treatment regimens were examined. Persistence was measured as months to discontinuation or modification, and adherence was measured as proportion of days covered (PDC). RESULTS:  The study included 1637 patients. Most patients initiated treatment with a monotherapy (93.8%). PDE-5is and ERAs were used in 70.0% and 26.8%, respectively, of initial treatment regimens. Of patients who discontinued (n=443) or modified (n=581) their initial regimen, 78.9% did so within one year (mean±SD 7.6±9.0 months, median 4.0). Combination therapies comprised 42.7% (248/581) of second regimens. Patients initiating combination therapy usually did so within six months (55.4%). ERAs were associated with higher PDC (0.8±0.4 vs. 0.6±0.4, p<0.001) and persistence (9.5±10.8 vs. 7.5±8.6 months, p<0.01) than PDE-5is. Combination therapies were associated with greater persistence than monotherapies (11.7±11.1 vs. 7.4±8.8 months, p<0.01). CONCLUSIONS:  Patients with PAH most often initiated treatment with monotherapies, commonly PDE-5is in spite of lower adherence and persistence than ERAs. Most patients remained treated with monotherapies. Therapy adjustments to initial regimens occurred early and in the majority of patients.