A method for sampling cytological brushings of human nasal mucosa using phase-contrast microscopy is detailed and the modes for counting the ciliary beat frequency (CBF) are reviewed. To test the reproducibility of our method, we performed two sampling procedures on subsequent days on each of 19 volunteers and patients. The total volume of harvested cells, the number of beating ciliated cells, and the CBF were assessed. Since there are some differences present in subsequent cell samples, our findings indicate that it may be better to critically evaluate a single sampling procedure in order to establish a correct clinical diagnosis, especially if the number of harvested cells is small. The need to standardize methods for counting the CBF to achieve comparable results is stressed.