Objective.To evaluate the safety and efficacy of intravenous golimumab (GOL) in patients with active ankylosing spondylitis (AS).Methods.In a phase III, randomized, double-blind, placebo (PBO)-controlled trial, 208 patients were randomized (1:1) to intravenous (IV) infusions of GOL 2 mg/kg (n = 105) at weeks 0, 4, 12, and every 8 weeks, or PBO (n = 103) at weeks 0, 4, and 12, with crossover to GOL at Week 16. The primary endpoint was ≥ 20% improvement from baseline in the Assessment of Spondyloarthritis International Society Criteria (ASAS20) at Week 16. Secondary endpoints included ASAS40, ≥ 50% improvement in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI50), and change in the Bath Ankylosing Spondylitis Functional Index (BASFI) at Week 16. Safety was monitored through Week 28.Results.Significantly greater proportions of GOL-treated patients had ASAS20 response at Week 2 (37.1% vs 19.4%; p = 0.005) and at Week 16 (73.3% vs 26.2%; p < 0.001). At Week 16, 41.0% of those receiving GOL achieved BASDAI50 compared with 14.6% of those taking PBO (p < 0.001), and the GOL group had greater mean improvement in BASFI (−2.4 vs −0.5; p < 0.001). Through Week 16, 23.3% of patients in the PBO group and 32.4% of patients in the GOL group had ≥ 1 adverse event (AE); infections being the commonest type of AE. Through Week 28, two GOL-treated patients had a serious AE.Conclusion.GOL 2 mg/kg administered IV at weeks 0, 4, and every 8 weeks significantly reduced the signs and symptoms of AS in adults. AE were consistent with other antitumor necrosis factor therapies, with no new safety signals (Clinicaltrials.gov: NCT02186873).