The aim of the study was to evaluate the efficacy of infliximab (IFX) treatment, 5 mg/kg every 6 weeks, in patients with active ankylosing spondylitis (AS) and to determine whether IFX dose reduction and interval extension, 3 mg/kg every 8 weeks during the second year sustained the treatment effect. The study was started in 2003 an finished in 2008.