In the immotile cilia syndrome, transmission electron microscopy of the cilia shows abnormalities in the arrangement of the central pairs of tubules and in the dynein arms of the peripheral tubules, or in the radial spokes, We studied four nonrelated children, 9/12, 5, 6, and 6 years old, with situs inversus and a history of chronic sinusitis and bronchitis (Kartagener's syndrome) and four children in the same age group and with the same history, but without situs inversus. Under the phase contrast microscope no motile cilia were seen in the four patients with Kartagener's syndrome and in two of the four other children. Transmission electron microscopy showed aberrations in the cilia (absence of dyneim arms, random orientation of central tubules) in the patients with Kartagener's syndrome. Scanning electron microscopy revealed differences in morphology and arrangement of cilia between patients and controls. In the patients much more mucus was present on the mucosal surface. Furthermore, the cilia were in a state of disorder, with a multidirectional orientation instead of the parallel orientation seen in controls.