The outcome was studied in 100 patients with adult-onset primary ankylosing spondylitis (AS). After a mean disease duration of 16 yr, 51.5% of the patients were employed in full-time work. Cessation of work occurred at a mean disease duration of 15.6 yr, and was significantly associated with female sex, low levels of education, acute anterior uveitis, 'bamboo spine' and the co-existence of non-rheumatic diseases. Functional outcome was studied by analysing activities of daily living, and revealed similar findings in males and females. Most of the loss of function occurred during the first 10 yr of disease, and correlated significantly with the occurrence of peripheral arthritis, spinal X-ray changes of AS and development of 'bamboo spine'. After > 20 yr of disease, > 80% of the patients still complained of daily pain and stiffness, and > 60% reported daily use of drugs.