Primary ciliary dyskinesia is a genetically determined disorder characterized by immotility or poor motility of the cilia in the airways and elsewhere. Certain specific defects in the ciliary axoneme can be found, which are pathognomonic of the syndrome. The defects include missing dynein arms, abnormally short dynein arms, spokes with no central sheath, missing central microtubules, and displacement of one of the nine peripheral doublets. We have reviewed 19 cases of primary ciliary dyskinesia diagnosed by transmission and scanning electron microscopy. The age distribution ranged from five to 15 years, and there were six males and 13 females. All 19 cases had abnormal cilia which consisted of Ia (three cases), Ib (three cases), isolated Id (three cases), isolated II (one case), isolated III (two cases), and Id + other types (seven cases), according to Sturgess' classification. The most pronounced clinical manifestations are chronic paranasal sinusitis (52%) and chronic bronchiectasis (52%), followed by bronchopneumonia (26%), chronic bronchitis (21%), and nasal polyps (15%).