To elucidate the effects of long term ethanol intake on the parotid gland, light and electron microscopic observations of the parotid glands from male Wistar rats that had been given 20% ethanol ad lib instead of water were carried out. The findings were compared with the changes in the pancreas previously reported (Kakizaki et al. 1987). The results were as follows: (1) Severe lesions involving lobular units of the parotid gland were found in three rats exposed to ethanol. (2) From the early stages of ethanol ingestion, the lateral interdigitations of acinar cells widened irregularly. In the striated ducts, basal enfoldings became also irregular and short, while the mitochondria (which were a slender rod shape and arranged parallel to the basal enfoldings in control rats) became swollen, developed a dark matrix, a decrease in the cristae, and showed random arrangement. (3) Later, both tortous proliferation of the intercalated ducts and destruction as well as irregular lamination of the basal lamina of the striated ducts were observed frequently. (4) The animals developing severe morphological changes in the pancreas following ethanol ingestion were different from the animals developing severe changes in the parotid gland.