Long-term exposure of cigarette smoke or air pollutants to human can induce damages in the airway mucociliary function and can be closely related to the irritation and sputum formation in the respiratory system. This study was undertaken to investigate whether rat trachea can be used as a tool for evaluating the cigarette smoke quality. It was identified that, through the examination with inverted microscope, ciliary beating in 1 mm long cut of nat trachea ring was continued for at least 48 hours in saline solution at $25^{circ}C$. The ciliostasis time in a KCN solution as a positive control was decreased with increasing the concentration of KCN. There were no significant differences in the ciliostasis time by body weight and individual variation of rats. Ciliotoxicity of whole smoke trapped in saline was not significantly changed by aging for more than 6 hrs. The ciliostasis time was in inverse proportion to the number of sample cigarettes applied. As moisture in the cigarette was increased, ciliostasis time was linearly increased. Therefore, these data indicate that the ciliotoxicity test using rat trachea in vitro can be applied to evaluate the cigarette smoke quality and to search factors for the irritation and sputum formation by cigarette smoke as well as air pollutants.