This randomized, double-blind, placebo-controlled study evaluated the safety and efficacy of tocilizumab (RoActemra/Actemra) in patients with ankylosing spondylitis (AS) who had an inadequate response to previous tumor necrosis factor (TNF) antagonist therapy. Patients were randomized to receive tocilizumab at a dose of either 8 mg/kg or 4 mg/kg intravenously (iv) or placebo every 4 weeks for 24 weeks. The double-blind treatment period was followed by open-label treatment with tocilizumab 8 mg/kg iv every 4 weeks until Week 104 for all patients.