Background: Hidradenitis suppurativa (HS) is a chronic inflammatory skin condition characterized by recurrent abscesses, nodules, and fistulous tracts. Recently, novel staging systems, including sonographic scoring system of hidradenitis suppurativa (SOS-HS), have been widely introduced in HS. Objective: To assess the efficacy of SOS-HS compared with Hurley staging and modified sartorius scoring (MSS) system and determine the necessity of ultrasound evaluation. Methods: A radiologist performed an ultrasound evaluation, and three dermatologists reviewed the images and videos. Clinical characteristics, including staging and demographic data, were recorded by three dermatologists. The correlation of each staging system and the significance of vascularity (Doppler mode) and lesion depth on sonography were statistically analyzed. Results: Among the 46 patients, 34.8% were classified as stage 1 and 3, and 30.4% were classified as stage 2 in the SOS-HS system, which was statistically higher than the Hurley staging (p＜0.0005). MSS score increased according to the SOS-HS stages (p＜0.0005, p=0.001). Vascularity and depth of involvement also increased with SOS-HS and Hurley staging. Conclusion: Sonographic examination can be applied in HS severity assessment and documentation of the clinical characteristics of each lesion in detail. Special tools, such as Doppler mode and depth assessment, can also be useful in HS evaluation. (Korean J Dermatol 2021;59(8):587∼595)