Background Hidradenitis suppurativa (HS) is a severe chronic inflammatory follicular disease characterized by nodules and abscesses affecting apocrine gland-bearing regions. HS is not well-controlled with conventional medical therapies such as topical therapy, oral antibiotics and retinoids, however, abrogation of tumour necrosis factor-α (TNF-α) function has proven effective in some patients. Objective To assess the safety and efficacy of the interleukin-12/23 inhibitor, ustekinumab for treatment of HS in three patients with moderate-severe disease. Methods The subjects received 3-45 mg subcutaneous injections of ustekinumab at 0, 1 and 4 months. Improvement was assessed by the dermatology life quality index (DLQI), visual analogue scale of pain (VAS) and physician's global assessment (PGA) at each monthly visit. Results Prior to treatment, subjects had moderate-severe HS (Hurley stage II-III) with a DLQI score between 8 and 12. At 6 months, one patient showed complete disease remission, while a 25-49% improvement was seen in a second patient and no change in a third. A moderate but statistically significant relationship was observed between VAS and DLQI scores (r = 0.75; P <0.01). Conclusion Ustekinumab may provide a safe and effective new treatment strategy for HS in some patients. Interleukin 12/23 inhibition is a potential therapeutic option for patients in which other therapies prove ineffective.