Transmission electron microscopy of nasal cilia was performed in three patients, two of them siblings, with repeated respiratory infections. Number of microtubuli and dynein arms were within normal limits and they had an ordered arrangement except for a disarray of the microtubuli in some areas of the biopsies from two of the patients. In the normal areas radial spokes and sheaths were easily found but nexin links could not be discerned in any of the patients. The orientation of the cilia was partly random. As all patients repeatedly and constantly had very low nasal NO (range 9-15 ppb; normal findings for persons <10 years old are > 50 ppb), the diagnoses were very likely primary ciliary dyskinesia (PCD). Absence of nexin links may be an ultrastructural variant of PCD. Deficiency of these structures might be the cause of the microtubular disarray observed in some areas of the biopsies.