BACKGROUND: Moderate-to-severe scalp psoriasis has not been evaluated in prospective trials of patients without moderate-to-severe body psoriasis. OBJECTIVE: Evaluate the efficacy and safety of secukinumab in moderate-to-severe scalp psoriasis. METHODS: In this 24-week, double-blind, phase 3b study, 102 patients were randomized 1:1 to subcutaneous secukinumab 300 mg or placebo at baseline, weeks 1, 2, and 3, and then every 4 weeks from week 4 to 20. The primary efficacy variable was 90% improvement of Psoriasis Scalp Severity Index (PSSI 90) score from baseline to week 12. RESULTS: At week 12, PSSI 90 (secukinumab 300 mg vs placebo, 52.9% vs 2.0%) and Investigator's Global Assessment modified 2011 scalp responses of 0 or 1 (secukinumab 300 mg vs placebo, 56.9% vs 5.9%) were significantly greater with secukinumab 300 mg than placebo (P < .001 for both). In addition, significantly more patients achieved complete clearance of scalp psoriasis at week 12 with secukinumab 300 mg than placebo (35.3% vs 0%; P < .001). The median time to 50% reduction in PSSI score was 3.29 weeks with secukinumab 300 mg. The safety profile of secukinumab was consistent with previous phase 3 studies. LIMITATIONS: There was no active comparator arm. CONCLUSION: Secukinumab is efficacious and well-tolerated for patients with extensive moderate-to-severe scalp psoriasis.