Women who have Kartagener's syndrome (primary ciliary dyskinesia) may or may not be fertile. The bronchial mucociliary clearance is reduced markedly in most of these women; this has led investigators to the conclusion that the cilia in the respiratory tract are immotile, and that "beating cilia may have no indispensable role in the female reproductive tract." Yet motile cilia are considered by many workers to be essential for normal ovum transport. More recently, bizarre ciliary motion has been described in the respiratory cilia of Kartagener's women. Our hypothesis was that the dyskinetic ciliary activity (or immotility) would be the same in both the respiratory and reproductive tracts and thus explain the fertility (or lack of it) in Kartagener's women. This report shows an identical ultrastructure and absolute immotility of cilia in both the respiratory tract and reproductive tract of a woman with Kartagener's syndrome who has never conceived. From this concordance, we suggest that the fertility of Kartagener's women is explained by the dyskinetic motion of oviductal cilia, and that the ciliated endosalpinx is essential for human reproduction.