The effects of chronic ethanol ingestion combined with fat-rich, protein-rich or carbohydrate-rich diets on the histology of the intact rat pancreas were studied. 192 male Wistar rats were randomly divided into four different dietary groups. Half of each group received 15% (v/v) ethanol in their drinking solution and the rest were used as controls and given tap water. After a 12-week diet period the pancreas were removed and histological specimens were stained with hematoxylin and eosin. No significant difference was observed between the groups in occurrence of edema, but inflammatory cells were found in (9/24) rats in the fat-rich group receiving water (p less than 0.01. In the fat-rich diet group receiving ethanol this finding was observed in 5 of 24 rats. In these groups slight parenchymal cell necrosis was also observed in conjunction with the inflammatory cells. All specimens in the other groups were normal. It is suggested that inflammatory changes caused by a fat-rich diet may be due to unknown toxic effects of this diet.