Summary Using a microphoto-oscillographic technique the authors studied ciliary beating of nasal epithelial cells from 11 patients with the ‘immotile cilia syndrome’ (Kartagener's syndrome) and from normal controls. Ciliary motility was found in all patients, except one. Although the patients had a significantly reduced number of cells with motile cilia, one-third of all ciliated cells showed motility. The beating frequency was normal, but the motility pattern was highly abnormal, with a predominance of asynchronous motility in the patients. These results suggest that the lack of dynein arms in cilia in these patients only is partial and that direct observation of ciliated cells, obtained by gentle scraping on the nasal mucosa, may be a suitable screening test for early diagnosis of this syndrome.