OBJECTIVES: Qualitative interview aimed to develop a PRO questionnaire that allows assessment of HAE acute attacks. METHODS: Open-ended qualitative interviews were performed with HAE patients in Argentina (n=10) and the US (n=33); these data were used to develop the first draft questionnaire.  Subsequently, more in-depth qualitative interviews were performed with HAE patients in the UK (n=10), Brazil (n=10), Germany (n=11) and France (n=12).  Patients who had experienced abdominal, cutaneous or laryngeal attacks of varying severity levels were recruited.  Patients initially discussed their experience of HAE attack symptoms, impacts and treatments in an open-ended manner.  Cognitive debriefing of the PRO was then performed to assess patient understanding and relevance of questionnaire items. RESULTS: Most commonly reported abdominal attack symptoms include pain, vomiting, stomach swelling, diarrhoea and nausea.  Cutaneous attacks caused skin swelling, pain and redness.  Laryngeal attacks led to difficulty breathing, voice change and difficulty swallowing.  Patients also discussed attack triggers, warning signs, impacts and treatment options.  Elicited concepts were mapped onto the PRO, which was revised to include all aspects of importance to HAE patients.  Cognitive debriefing aided in the revision of the questionnaire. CONCLUSIONS: Data from the qualitative interviews were used to develop an expanded conceptual model capturing all aspects of HAE.  The PRO was revised to ensure all concepts of importance to HAE are captured.  The questionnaire can be considered a valid tool for the long term assessment of the HAE patients.