Twenty seven patients with clinical evidence of lack of mucociliary activity of cilia, which include Kartagener's syndrome and termed in recent years immotile cilia syndrome or primary ciliary dyskinesia, were studied by a newly developed microphoto oscillografic technique, to determine different qualities in the ciliary motility pattern in vitro. Abnormal ciliary motility was compared to the findings at transmission electron microscopy. The patients could be allocated to groups, characterized by different abnormalities in ultrastructure and function. One patient who lacked both inner and outer dynein arms, and had total ciliary immotility. Eight who only lacked outer dynein arms had a low beating frequency, reduced number of cells with motile cilia and ciliary asynchrony. Seven with microtubular disarrangement (spoke defect) had cilia which beat asynchroneously and with short, stiff strokes. Two patients had random orientation of ciliary axes and one supernumerous microtubules, all were characterized by slight ciliary asynchrony. Eight patients had normal cilia ultrastructure, but an abnormal beating pattern, usual characterized by hyperfrequent and trembling ciliary movements (hypermotile). These groups seem to constitute separate types of congenital ciliary defects.