Fibrocystic changes in the upper lung lobes are a rare visceral manifestation of ankylosing spondylitis. The impaired bronchopulmonary clearance in bronchial, pulmonary or pleural cavities predisposes to secondary microbial colonisation. Two cases are reported--one patient proved to have non-tuberculous mycobacterial disease caused by M. kansasii, the other developed an aspergilloma.