This study will represent the sponsor's first controlled study of etanercept in Chinese subjects with Ankylosing Spondytitis (AS). This trial is designed to assess the safety and efficacy of etanercept compared to placebo in the treatment of patients with AS.

Multicenter, double-blind, randomized, parallel and placebo-controlled outpatient study. The study consists of 2 parts: part A is a 6-week double-blind treatment period and part B is a 6-week open-label treatment period. During part A of the study, subjects will be randomly assigned to 1 of 2 treatment regimens: 2 etanercept 25 mg or placebo once weekly, administered subcutaneously (SC). After the completion of part A, all subjects will receive 2 etanercept 25 mg once weekly. The use of placebo as a control in part A is necessary to allow a valid comparison and to provide a quantitative assessment of effect.

Inclusion Criteria:

1. Must be of Chinese ancestry and living in China.
2. Diagnosis of AS, as defined by Modified New York Criteria for Ankylosing Spondylitis.
3. Active AS at time of enrollment, defined by average of visual analog scale (VAS) values for duration and intensity of morning stiffness 30 and two of the following: VAS for patient global assessment 30; average of VAS for nocturnal and total pain 30; BASFI greater than or equal to 30 (all scores on a scale of 0 to 100).

Exclusion Criteria:

1. Complete ankylosis (fusion) of spine.
2. Previous treatment with etanercept, antibody to Tumor Necrosis Factor a (TNFa), or other TNFa inhibitors or other biologic agents.
3. Use of disease modifying antirheumatic drugs (DMARDs) other than hydroxychloroquine, sulphasalazine, and methotrexate within 4 weeks of baseline. Subjects treated with hydroxychloroquine, sulphasalazine, and methotrexate may continue these drugs during this study but doses must be held stable for 4 weeks before baseline examination and for the duration of the study.