Tracheobronchial clearance was studied in twenty patients who fulfilled suggested criteria of the immotile-cilia syndrome and in eight other patients suspected of suffering from the syndrome, but who did not fulfill the criteria. Clearance was studied using 6 micrometers teflon aerosol particles tagged with 99mTc and external measurement of the radioactivity. The criteria were based on combinations of a typical history of bronchitis, rhinitis and sinusitis since childhood, hereditary data, situs inversus, sperm immotility and characteristic defects of respiratory tract cilia and sperm tails. All patients who fulfilled the criteria had an extremely slow, probably no, tracheobronchial mucociliary clearance, whereas all those who did not fulfill the criteria had some clearance. Evidently the diagnosis immotile-cilia syndrome can be obtained without clearance measurements in typical cases, but such measurements are of value in atypical cases, especially for excluding the syndrome.