© 2019 British Association of Dermatologists Background: Hidradenitis suppurativa (HS), also referred to as acne inversa, is a debilitating skin disease characterized by inflammatory nodules, chronic abscesses and tunnels (fistulae and sinuses). The association with pilonidal sinus disease (PSD) is frequently reported but not well documented. Objectives: To determine the prevalence and characteristics of inflammatory skin lesions located in the intergluteal fold (IGF) of patients with HS. Methods: This was an international multicentre retrospective cross-sectional study based on data collection from a large cohort of patients with HS with and without histopathology. Results From a total of 2465 patients with HS included in the study, 661 (27%) reported lesions in the IGF. These patients were significantly more often smokers and had more severe HS. Of the 238 patients with an available clinical diagnosis, intergluteal-HS (IG-HS) was diagnosed in 52 patients (22%) and PSD was diagnosed in 186 patients (78%). IG-HS was associated with the localization of HS in the proximity of the IGF, including the buttocks, genitals and the anus. There was a possibility of misclassification bias in this study as a clinical/image-based diagnosis or histopathology of the IGF lesions was not always available. Conclusions: The high prevalence of PSD suggests a strong link between both entities. Therefore, it may be useful to identify common pathophysiological mechanisms and develop common therapeutic strategies.