Pulmonary changes in 100 patients suffering from ankylosing spondylitis were studied. There were 85 men and 15 women with an average age of 48 years (range 29 to 72 years). The mean duration of the disease was 18 years (range 4 to 37 years). The highest percentage of patients (66%) was aged 40 to 60 years. Pleuropulmonary changes were found in 21% of cases. Of these, 11% were due to pulmonary and pleural tuberculosis and the remaining 19% to nonspecific inflammatory processes. Fibrobulous changes affecting the apical region of the lungs were found in one patient with rigid spine and thoracic cage 13 years after the onset of the disease.