Using a photometric method of measuring ciliary beat frequency, the effect of temperature on ciliary activity was investigated. A linear increase in ciliary beat frequency between 19 degrees and 32 degrees C was found. Between 32 degrees and 40 degrees a plateau was reached in which temperature did not significantly affect frequency and above 40 degrees C the frequency began to decline. It is concluded that nasal cilia are not critically dependent upon temperature in the range 32 degrees and 40 degrees C, the temperature range in which this tissue normally operates.