Hidradenitis suppurativa (HS) is a chronic, inflammatory condition that can have a large negative impact on health-related quality of life (HRQOL). A reliable and validated measure of HS-specific HRQOL in clinical studies is needed. To develop and validate the Hidradenitis Suppurativa Quality Of Life (HiSQOL©) scale, for clinical trial measurement of HS-specific HRQOL. In stage 1, qualitative concept elicitation interviews were conducted with patients with HS in Denmark (n = 21) and the U.S.A. (n = 21). In stage 2, cognitive debriefing interviews were performed with U.S. (n = 30) and Danish patients with HS (n = 30). In stage 3 an observational study of 222 patients with HS in the U.S.A. was conducted for item reduction, measure validation and assessment of psychometric properties. In stage 4, an observational study of 215 patients with HS in Denmark was conducted to confirm the psychometric structure derived in stage 3. In both studies the Dermatology Life Quality Index, Hospital Anxiety and Depression Scale and numerical rating scale for pain were also included. In concept elicitation, 99 items were generated, which were reduced to 41 after removing duplicates. In cognitive debriefing, two items were added and one item removed. A 42-item instrument was psychometrically assessed. Based on psychometric analyses and patient input, the instrument was reduced to 17 items that had strong psychometric properties in both the U.S. and Danish samples. The HiSQOL is a reliable and valid instrument to measure HS-specific HRQOL in clinical trials. © 2019 British Association of Dermatologists.