Seventy-six patients treated for ankylosing spondylitis at the Rheumatism Foundation Hospital during the 1950s were re-examined. The mean duration of the disease was 30.5 years. The main interest was in the clinical and radiological progression of the disease, functional and working ability and the number of complications and their severity. The results seem to show that the long-term prognosis for AS is good, on average. A detailed description of the results is presented.