Anthracite coal briquette gas is one of the most ubiqutous toxic gases in Korea associated with heating in winter : it contains mixtures of CO, H₂S, NO, NO₂ and SO₂. Although a number of experimental studies were made on the toxic effects of individual gases, no study has been reported on the toxic effects of anthracite coal briquette gas itself. The purpose of this experiment is to elucidate the pathological changes of respiratory tract in rabbits following the exposure to actual briquette gas. A total of 37 rabbits were used including 7 control animals. The experimental animals were divided into three groups according to the time of exposure : 5 rabbits were exposed to the gas for one hour, 13 rabbits for two hours and 12 rabbits for three hours. The results observed were as following texts : 1) Anthracite coal briquette gas is mixed gas containing CO, NO₂, NO, SO₂ and H₂S, the concentration of which is within the maximum permissible level for industrial workers except for CO. 2) Larynx and tracheobronchial tree showed more predominant findings than nasal mucosa in basal cell hyperplasia(p<0.01), and than nasal mucosa and lung in edema and congestion(p<0.025). The cilia loss, however, was mainly observed in nasal mucosa(p<0.05). The pathology of lung was almost negligible. 3) Nine rabbits were expired during exposure : two were from 2 hours exposure group and seven were from 3 hours exposure group, in which two revealed severe pulmonary edema and other two showed intra-alveolar hemorrhage. The pathological changes appeared to be caused by toxic effect of irritant gases -SO₂, NO, NO₂. Furthermore, co-existing gases-CO, H₂S might also work as a synergist to induce the above pathological findings.