Background and objectives Efficacy of adalimumab for ankylosing spondylitis (AS) has been established for Western populations but not in the Chinese population. This study is the first to evaluate the efficacy and safety of adalimumab in Chinese patients with AS. Methods Chinese adults with active AS who had an inadequate response or were intolerant to 1 non-steroidal anti-inflammatory drugs were randomised to adalimumab 40mg (N=229) or matching placebo (N=115) subcutaneously every other week (EOW) for 12weeks, followed by a 12-week open-label adalimumab 40mg EOW phase. The primary efficacy endpoint was the percentage of patients meeting the Assessment in Spondyloarthritis International Society (ASAS20) response criteria at week 12. The recently developed AS Disease Activity Score (ASDAS), as well as efficacy measures of spinal mobility, disease activity, physical function and quality of life were evaluated. Results At week 12, adalimumab treatment resulted in a significantly greater percentage of ASAS20 responders than placebo (67.2% versus 30.4%, respectively; p<0.001). Differences in ASAS20 were observed as early as week 2 (42.8% vs 6.1%, respectively; p<0.001). The percentages of patients achieving ASAS40, ASAS 5/6 and ASDAS inactive disease were significantly greater with adalimumab than placebo at week 12 (all p<0.001). Tuberculosis was reported in one patient. No cases of malignancy, lymphoma, demyelinating disease or lupus-like syndrome were reported during the study. Conclusions Adalimumab significantly reduced the signs and symptoms, improved physical function and quality of life of Chinese patients with active AS, and was generally safe and well tolerated in this population.