To develop criteria to aid in the diagnosis of primary ciliary dyskinesia (PCD) we analyzed quantitatively the incidence and the range of ciliary ultrastructural abnormalities in healthy subjects and in patients with respiratory tract disease. The beat frequency and ultrastructure of nasal respiratory tract cilia, including ciliary orientation, were measured in 62 healthy subjects (31 nonsmokers, 20 exsmokers, and 11 smokers), ranging in age from 1 to 76 yr, and in 51 patients with respiratory tract disease. In healthy subjects, ciliary beat frequency (CBF) ranged between 9.6 and 15.3 Hz, the incidence of microtubule defects varied between 0 to 9%, the mean number of inner dynein arms per cilium ranged from 3.0 to 7.1, and the mean number of outer dynein arms per cilium ranged from 7.4 to 9.0. The deviation of cilia in healthy subjects varied between 8 and 29 degrees. By comparing the data for ciliary defects in healthy subjects with the data obtained from patients with respiratory disease, we identified two patient groups: patients with PCD (n = 31) and patients with respiratory tract disease not due to PCD. For comparison with the PCD patients, a group of 20 patients with bronchiectasis was selected and analyzed. Patients with PCD had significantly lower CBF (p < 0.001), significantly higher incidences of peripheral and central tubule defects (p < 0.01), and greater ciliary disorientation (p < 0.005). There was a strong correlation between CBF and the number of outer dynein arm numbers, but not with inner dynein arm numbers, suggesting that inner and outer dynein arms may play different functional roles in producing ciliary motility.(ABSTRACT TRUNCATED AT 250 WORDS)