It is known that cadmium exposure to human bodies is very harmful and potentially toxic to liver, kidney, testis and lung. Therefore, the authors had undertaken to examine the chronic effects of cadmium chloride on the fine structures of rat nasal mucosa. Adult healthy male rats(Wistar strain), 200~250gm weight, were used as experimental animals. The experimental rats were injected intraperitoneally with 3.75mg/kg of cadmium chloride, per one week for 10 weeks. Experimental animals were sacrificed at 1 day, 1 week, 2 weeks and 4 weeks after cadmium chloride administration for 10 weeks. For the transmission electron microscopic examination, the ultrathin sections were made and stained with uranyl acetate and lead citrate. The results were as follows : 1) 24 hours after 10 weeks of cadmium chloride administration. Ciliated columnar cells and non-ciliated cells of rat nasal mucosa showed dilated and segmented cisternae of rough endoplasmic reticulum, numerous lysosomes and reduction of mitochondrial cristae in the cytoplasm. 2) 1 week and 2 weeks after 10 weeks of cadmium chloride administration. The non-ciliated cells revealed reduced mostly mitochondrial cristae, numerous autophagic vacuoles, severely dilated cisternae of rough endoplasmic reticulum. And large amount of polyribosomes were spread over the cytoplasm. The ciliated columnar epithelium showed the damages of mitochondria, numerous polyribosomes, atrophy of Golgi complex and segmented sacculated cisternae or rough endoplasmic reticulum. 3) 4 weeks after 10 weeks of cadmium chloride administration. Nasal epithelial cells of the rat nasal mucosa showed nearly normal cytoplasmic organelles similar to that of the control rats. Consequently it is suggested that cadmium chloride can induce degenerative changes in the fine structure of the nasal epithelium.