Abstract: Female clean SD rats were divided into two groups. Group I，13 rats were layed in the isolator for passive smoking for two hours per day. Group Ⅱ , as control group, 10 rats were layed in the isolator without passive smoking for two hours per day. Twenty days later, bronchoalveolar lavage fluid (BALF) were collected for count-ing and sorting the inflammatory cells； the surface of the main right bronchus was ob-served by scanning electron microscope； lung tissues were observed by light microscope. The results showed that the number of total cells in BALF in Group I [(46.1 ±28.3) × 10⁶/L] was higher than that in Group Ⅱ [(17. 7 ± 9. 9) ×10⁶L] (P<0. 05). The inflammatory cells were infiltrated in the wall of small airways and lung tissues； the fimbme of columnar epithelial cells of airway were failed and in disorder, some of them shed. The results suggested that the stimulation of smoke induced increase of inflammatory reaction of the airway and the function of fimbriae decreased, these may lead to the injury of the airway.

Key words: Passive smoking, Bronchoalveolar lavage fluid, Inflammatory reaction, Pathological morphology, Rat