OBJECTIVES:  PAH-SYMPACT^® is a patient reported outcome (PRO) instrument; the draft consists of 16 symptom and 25 impact items. The PRO was developed based on interviews with patients with pulmonary arterial hypertension (PAH) following the process outlined in the FDA’s PRO guidance. Its psychometric characteristics are being evaluated using data from SYMPHONY - a phase IIIb PAH study with macitentan. The goal of the analyses was the finalization of item content and domain structure while ensuring the instrument is clinically and patient relevant. METHODS:  In SYMPHONY, patients completed generic and disease-specific questionnaires while clinicians provided assessment of severity and changes in symptomatology. Item performance, Rasch and Factor analyses of baseline data were used together with expert input to select the final items and define the domain structure. RESULTS:  Data from 278 patients (79% female, mean age 60 years) were included in the analysis. 40% and 59% of patients were in WHO functional class II and III, respectively, and 41% were receiving background therapy with a phosphodiesterase type-5 inhibitor. As expected for a moderately severe population, some items had high (>50%) floor effects. Following removal of redundant or mis-fitting items, the final instrument has 11 symptom items (shortness of breath, fatigue, lack of energy, swelling in ankles/legs, swelling in stomach area, cough, heart palpitations, rapid heartbeat, chest pain, chest tightness, lightheadedness) across 2 domains (cardiopulmonary and cardiovascular symptoms), and 11 impact items (walk slowly/quickly on flat surface, walk uphill, carry things, light chores, need help, wash/dress self, think clearly, sad, worried, frustrated) across 2 domains (physical impacts and cognitive/emotional impacts). Compliance in completing the questionnaire was 83%. CONCLUSIONS:  PAH-SYMPACT^® is a clinically and PAH-patient relevant instrument. This PRO has the potential to become an important outcome measure for PAH in both clinical practice and clinical trials.