Anthracite coal briquette gas is a unique environmental pollutant gas ubiquitous in Korea and is a mixed gas containing CO, CO₂, NO₂, and H₂S. Numerous studies have been carried out on the health effect of major air pollutants. It is of great important to clarify the damage to mucociliary transport system caused by exposure to anthracite coal briquette gas. The purpose of this study is to clarify the effects of anthracite coal briquette gas on the respiratory mucosa by ultrastructural study of the nasal and tracheal mucous membrane of rabbit which was exposed to anthracite coal briquette gas. Thirty rabbits were used and divided into 3 groups ; 3 were control group, 12 were short term exposure group and 15 were long term exposure group. The results were as follows ; 1) In short term exposure group, light microscopic findings of nasal and tracheal mucosa showed focal loss of cilia ad mild epithelial damage. The pathologic changes were more severe in nasal mucosa and in 3 hours exposure group. Electron microscopic findings of nasal and tracheal mucosa showed mild pathological changes, ciliary distortion. 2) After 3 hours exposure to briquette gas, nasal mucosal cells recovered from the initial pathological change while tracheal mucosal cells did not recover within 7 days. Major ultrastructural findings in tracheal mucosa at 7 days after 3 hours exposure were increased secretory granules, functional fusion of cilia, occasional anatomical fusion of cilia, loss of cilia and increased number of mitochondria. 3) In long term exposure group, the pathologic changes became more severe proportionally to the duration of exposure. Three weeks exposure group showed the most prominent morphological changes among the experimental groups. Major ultrastructural changes were severe ciliary distortion, anatomical fusion of cilia and loss of cilia in scanning electron microscopy and irregular arrangement of basal bodies, focal loss of cilia, multiple formation of intracellular vacuole, increased growth of microvilli and increased number of mitochondria in trasmission electron microscopy. Anthracite coal briquette gas caused the ultrastructural changes on the respiratory mucosa especially in long term exposure group. The degree of the changes was proportional to the duration of exposure. These findings indicated that there was a mucociliary dysfunction in the respiratory tract exposed to briquette gas, and thus the briquette gas might initiate or prolong respiratory diseases.