We present 17 patients with a typical symptomatology of immotile cilia syndrome, seven of them with complete situs inversus. Firstly, a study of the nasal mucociliary transport was made by means of the radioisotopic technique with serum albumin-Tc99m. In all cases there was absence of transport. Secondly, we studied the ultrastructure of the nasal cilia. Defects in the dynein arms were frequently found (65%). In two cases (11%) there were no cilia; in two other cases the cilia were normal, and in another two cases alterations of the central pair of microtubules were seen. Ciliary complexes were detected in all cases. We conclude that in patients with chronic or recurrent infections of the airways without known cause we must initiate a study of the nasal mucociliary transport. If this is absent or decreased, study of ciliary ultrastructure should be carried out. If mucociliary transport is normal, immotile cilia syndrome is ruled out and ultrastructural study of the cilia is not required.