Background Hidradenitis suppurativa (HS) is a chronic inflammatory disease involving inverse recurrent suppuration (IRS). The epidemiology of the disease is not well described, with previous studies reporting prevalence estimates from 0·00033% to 4%. Objective To determine the prevalence of IRS in a large population-based survey. Methods Data were obtained from a general cross-sectional population study in Denmark. A validated self-administered questionnaire was used to identify IRS. Persons with the combination of outbreaks of 'boils' during the last 6 months in predefined areas and a minimum of two boils were identified. Results A total of 16 404 adults aged 30-89 years provided data and the overall prevalence of IRS was found to be 2·10% [95% confidence interval (CI) 1·88-2·32]; in men it was 1·58% (95% CI 1·29-1·86) and in women 2·56% (95% CI 2·21-2·86). No data for adults aged 20-29 years were included. The prevalence declined with age. The majority of cases (72·9%) had a body mass index of ≥ 25 kg m-2 and 77·7% were current or ex-smokers. The mean number of inflamed lesions was 6·5 (range 2-67) during the last 6 months. The lesions affected mostly the genitalia (43·4%) and groin (39·8%) for women and 'other places' (not specified) (78·8%) for men. Conclusions Data on IRS suggest that HS may be more prevalent than previously suggested, and the prevalence may be comparable to other major dermatoses, e.g. psoriasis. However, as no physician examination was done, the risk of recall and information bias is a major limitation. What's already known about this topic? Hidradenitis suppurativa is a chronic inflammatory disease. The previous estimates of hidradenitis suppurativa prevalence rates range from 0·00033% to 4%. What does this study add? Prevalence data for inverse recurrent suppuration were compatible with the diagnosis of hidradenitis suppurativa in a large population-based survey sample. Prevalence data were derived from a validated questionnaire.