A study was conducted of the clinical manifestations and ultrastructure in a series of seven patients with repeated pulmonary infections and infertility (3 cases with primary ciliary dyskinesia [PCD] and 4 with the young syndrome [YS]). Clinical and functional respiratory changes were more marked among cases of PCD. The seminogram showed azoospermia in cases with YS and hypospermia with marked hypomotility in cases with PCD. A nasal mucosa biopsy specimen was obtained from all patients to perform a transmission electron microscopy (EM) investigation. Patients with YS did not have pathognomonic ultrastructural changes, whereas patients with PCD had a large number of ciliary abnormalities (23.3% +/- 1.5%); 14% +/- 7% of them corresponded to nonspecific ciliary changes and the remaining abnormalities to congenital ciliary changes (ciliary disorientation in three cases, defective radial spokes in one case and microtubule transposition in one case). EM is a useful technique which is recommended for the differential diagnosis in this group of patients.