Hidradenitis suppurativa (HS) is a chronic, relapsing, and debilitating inflammatory disease associated with profound morbidity.In this multicenter study, we investigated the demographic and clinical features of HS and determined risk factors of disease severity.A total of 1221 patients diagnosed with HS from 29 centers were enrolled, and the medical records of each patient were reviewed.The mean age of disease onset was 26.2 ± 10.4 years and almost 70% (n = 849) of patients were current or former smokers. Mean disease duration was 8.9 ± 8.4 years with a diagnosis delay of 5.8 ± 3.91 years. Twenty-one percent (n = 256) of patients had a family history of HS. The axillary, genital, and neck regions in males and the inframammary region in females were more frequently affected (p < 0.05 for all). Acne (40.8%), pilonidal sinus (23.6%), and diabetes mellitus (12.6%) were the most prevalent associated diseases. Among systemic therapies, antibiotics (76.4%) were most common followed by retinoids (41.7%), surgical interventions (32.0%), and biologic agents (15.4%). Logistic regression analysis revealed the most important determinants of disease severity were male sex (odds ratio [OR] 2.211), and involvement of the genitals (OR 3.387) and inguinal region (OR 2.253). Patients with a comorbidity, longer disease duration, longer diagnosis delay, and a higher number of smoking pack-years had more severe disease.Our nationwide cohort study found HS shows demographic and clinical variation, and it may help broaden the understanding of HS and factors associated with disease severity.