In published reports, the incidence of pleuropulmonary involvement in ankylosing spondylitis varies from 0 to 30%. A review of the records of 2,080 patients with ankylosing spondylitis disclosed 28 who had pleuropulmonary manifestations that we believe are typical of those associated with ankylosing spondylitis (an incidence of 1.3%). Among these 28 patients, the most common abnormality was upper lobe fibrobullous lesions. Five had aspergillomas and two had infections-one caused by Mycobacterium kansasii and one by Mycobacterium avium. Three patients had transient pleural effusion of an exudate with normal sugar content. Two had nonspecific pleuritis, found on pleural biopsy. Thoracotomy for aspergilloma was followed by bronchopleural fistula in one of two cases--approximately the ratio found in the literature.