Background: Medical therapies for hidradenitis suppurativa (HS) are often ineffective. Tumor necrosis factor-a inhibitors may be a potential treatment for patients with moderate to severe HS. Objectives: We sought to evaluate the safety and efficacy of etanercept for patients with severe HS. Methods: We conducted a phase 11 clinical trial of etanercept (50 mg/wk subcutaneously) in patients with moderate to severe HS. Efficacy was measured using a Physician Global Assessment and several secondary physician- and patient-reported outcome measures. Responders were classified as those achieving at least a 50% reduction on the Physician Global Assessment score at week 12 compared with baseline. Results. Only 3 of the 15 patients who entered the study were classified as responders (response rate of 20%; 95% confidence interval: 4.3-48.1) based on the intention-to-treat analysis. Dermatology fife Quality Index scores improved slightly from a median of 19 to 15 (P = .02). Comparison of baseline with week-12 Physician Global Assessment scores, and secondary outcome measures of lesion counts and patient pain scores, failed to show statistically significant improvement. Etanercept was generally well tolerated: however, two patients discontinued the study as a result of skin infections at the site of hidradenitis lesions requiring oral antibiotics. Limitations: Lack of a control group and a small number of participants are limitations. Conclusions: Our study demonstrated minimal evidence of: clinically significant efficacy of etanercept (50 mg/wk subcutaneously) in the treatment of hidradenitis. Future studies using higher closes of etanercept are indicated; however, patients need to be carefully monitored for infection and other adverse events. Randomized, controlled trials will be necessary to demonstrate the risk-to-benefit ratio of tumor necrosis factor-a inhibitors in the treatment of hidradenitis. (J Am Acad Dermatol 2009;60:565-73.)