Biological therapy for ankylosing spondylitis (AS) has led to improved disease control beyond that of conventional treatments. International recommendations encourage clinicians prescribing biological treatments to register patients in national registers to collect information on outcome and toxicity. Patients with AS (n = 229) from the Register of Biological Treatment in Finland (ROB-FIN) with severe disease of long duration were followed-up for up to 24 months. Due to an active disease, one or more concomitant disease-modifying antirheumatic drugs (DMARDs) were used by 86% at commencement of biological therapy. This add-on strategy with infliximab led to a rapid pain relief and improvement of patient's and physician's global assessments, C-reactive protein/erythrocyte sedimentation rate, and swollen and tender joint counts within 6 weeks. Concomitant use of NSAID and oral corticosteroid was reduced. Corresponding results were documented at 3 months with etanercept, which was more recently approved for the treatment of spondyloarthropathies. Seventy-nine percent of the patients were ASAS 20 responders. A subgroup of AS patients with only axial involvement (n = 46) responded correspondingly. The first biological drug was discontinued in only 7% due to lack of efficacy and in 6% due to adverse events. Anti-TNF agents, often used in combination with DMARDs, appeared to have persistent effectiveness and limited toxicity in a real-life clinical setting in a cohort of Finnish AS patients with severe disease and long disease duration.