Purpose: Content validity is the extent to which a patient-reported outcome measure evaluates the concepts most relevant to a patient's condition and treatment. The St George's Respiratory Questionnaire (SGRQ) has been validated in a range of respiratory conditions. This study evaluated the content validity of the SGRQ in patients with severe asthma. Methods: A qualitative study, guided by a protocol, which included concept elicitation and cognitive debriefing of the SGRQ, was conducted in patients aged >= 18 years with history of severe asthma and blood eosinophil counts of >= 150/mu L (past month) or >= 300/mu L (past 12 months). Patients were recruited until saturation for concept elicitation was achieved (i.e. no additional concepts identified). Concepts identified by the patients were then mapped to the SGRQ. Results: 18 patient interviews provided concept saturation. Concept elicitation confirmed that the SGRQ includes the commonly reported asthma symptoms and their impact on daily life. In total, 89-100% of patients routinely experienced cough, nighttime awakenings, shortness of breath, chest tightness, sleep difficulty, phlegm/mucus, and wheezing. Patients reported asthma impacting daily and physical activities, mood and sleep. Cognitive interviewing confirmed that patients understood the instructions, items and response options in the SGRQ. Nearly half of the concepts in the SGRQ were endorsed by >= 12 patients; of the 17 items with scoring weights >= 85, 11 were mentioned by >= 12 patients. Conclusions: This study demonstrates that the SGRQ is a relevant, comprehensive and content-valid instrument to assess health status in patients with severe asthma. (C) 2017 Elsevier Ltd. All rights reserved.