Giant cell arteritis is a large vessel vasculitis presenting with headache, jaw claudication, musculoskeletal and visual involvement. Current treatment is glucocorticoids and anti-IL6 Tocilizumab in refractory disease. The objective of this study was to explore the impact of GCA and its treatment on peoples' health related quality of life (HRQoL), to inform the development of a disease-specific patient reported outcome measure (PROM) for use in clinical trials and practice.Participants from the UK and Australia, with biopsy- or imaging-confirmed GCA, were interviewed to identify salient aspects of HRQoL in relation to GCA and its treatment. Purposive sampling included a range of demographic and disease features (cranial, large vessel vasculitis (LVV)-GCA and visual involvement). Inductive analysis identified individual themes of importance, then domains. Candidate questionnaire items were developed from the individual themes, refined by piloting, cognitive interviews and a linguistic translatability assessment.Thirty six interviews were conducted to saturation with participants with GCA from the UK (25) and Australia (11). Mean age 74 years, 23 (63.9%) female, 13 (36.1%) visual loss and 5 (13.9%) LVV-GCA. Thirty-nine individual themes within five domains identified: Physical Symptoms, Activity of Daily Living (ADLs) and Function, Participation, Psychological Impact and Impact on Sense of Self and Perception of Health. Sixty-nine candidate items developed from individual themes; piloting and refinement resulted in a 40-item draft questionnaire.This international qualitative study underpins the development of candidate items for a disease specific PROM for GCA. The draft questionnaire is now ready for psychometric testing.