1. Sputum sols, obtained from patients with chronic obstructive pulmonary diseases, were applied to frogs' isolated palates and the effect on ciliary beat frequency was examined.
2. During clinical exacerbations, a significant number of asthmatic patients produced a distinct, slurry type of sputum, which induced ciliostasis. This ciliary inhibition largely disappeared with clinical improvement, at which time there was also a change of the type of sputum from slurry to mucoid.
3. Samples obtained from normal volunteers and from the great majority of the patients, excluding those with asthma, had no effect on ciliary beating.