We have developed an automated image analysis method to study the ciliary beat frequency of ciliated cells of the primary culture from rabbit trachea. The ciliated outgrowth image is digitized and the variation in optical density is automatically calculated for each selected area of interest. 32 measurements of ciliary beat frequency are, in this way, calculated simultaneously in 6 min. With this reliable device, some studies on baseline frequency of control culture have been carried out. There was no variation in the mean frequencies of ciliated cells of the primary culture of different tracheas in our culture conditions. Moreover, the values of ciliary beat frequency at the starting point of the outgrowth were similar to those at the periphery of the outgrowth. There is nevertheless a slow decrease in frequencies versus the duration of culture. We have also established that the frequency of ciliary beat of some cells fluctuates in a periodic pattern whereas the majority of the ciliated population beat in a stable way. The image analysis process allows us to perform a cartography of frequencies on the video display. It also allows us to have access to the frequency of one cilium. Our method therefore seems to be reliable and furthermore simple in the evaluation of the potential effect of inhaled toxic compounds on ciliated cells of mammalian respiratory tract.