Respiratory cilia and sperm flagella of nine Japanese patients with immotile-dyskinetic cilia syndrome were studied ultrastructurally by using a tannic acid-containing fixative. Respiratory cilia from two female patients with Kartagener's syndrome and one male patient with situs inversus and sinobronchitis were completely immotile and lacked both dynein arms. However, approximately 30% of the spermatozoa from the male patient were weakly motile. In four patients with immotile cilia syndrome without Kartagener's triad, immotile respiratory cilia generally lacked the inner dynein arms. Two clinically unusual cases, an 11-year-old boy and a 29-year-old woman with prolonged saccharin test, recurrent bronchitis, and bronchiectasia, possessed motile respiratory cilia. Ultrastructurally, both dynein arms were normal, but numerous defective central pairs (more than 50% and 70%, respectively) were seen, and the defect in the second case was similar to the transposition of microtubules reported by Sturgess et al (N Engl J Med 303:318-322, 1980). However, defects in the first case were unique and may be congenital. We propose a new type of dyskinetic cilia syndrome with defective central pairs. Additionally, nasal cilia from a 35-year-old man with immotile cilia syndrome contained excess large singlets within ciliary axonemes consisting of 17 protofilaments.