Specific antagonists of tumor necrosis factor (TNFalpha) have rapidly gain popularity for the treatment of ankylosing spondylitis (AS). The dose of etanercept has not been determined in Asia, especially in Korea. This study was designed to investigate the maintaining effect of low-dose (25 mg/week) etanercept in Korean patients with AS and after discontinuation, the duration to be aggravated. Patients who had active AS [Bath AS Disease Activity Index (BASDAI) > or =4] were treated with 50 mg of etanercept per week for 3 months. After that, for 6 months, the patients were treated with 25 mg of etanercept per week. We evaluated the serum erythrocyte sediment rate (ESR), C-reactive protein (CRP), and BASDAI every 1 month for 3 months and every 2-3 months during the remaining 6 months. After all schedules of treatment were finished, we reevaluated ESR, CRP, and BASDAI every 4 months until recurrence. Twenty-seven AS patients received etanercept. Twenty-three patients completed treatment for 3 months with a dose of 50 mg/week. Among them, 18 completed for 6 months with a dose of 25 mg/week and discontinued. Mean age was 30.0 +/- 5.4 years and mean disease duration was 7.5 +/- 6.5 years. These 18 patients were evaluated for BASDAI, ESR, and CRP every 4 weeks. After discontinuation, mean duration to recur was 9.2 +/- 6.1 weeks. Twenty-five milligrams of etanercept per week is effective enough to maintain remission in AS. After discontinuation, this effect was maintained by using a dose of 50 mg of etanercept per week.