The clinical manifestations of primary ciliary dyskinesia (PCD) — recurrent sinopulmonary infection and male sterility — have been attributed to defects in the ultrastructure of the central core (axoneme) of cilia and sperm tails. In the respiratory tract, these structural defects impair ciliary motility and coordination, resulting in reduced mucociliary clearance. Defective ciliary function and structure were first reported as a cause of recurrent respiratory disease by Afzelius and coworkers,1 , 2 who noted decreased ciliary motility in patients with Kartagener's syndrome and suggested the term immotile-cilia syndrome. Subsequent studies of ciliary motility and ultrastructure have revealed a range of patterns of. © 1990, Massachusetts Medical Society. All rights reserved.