124 male Wistar rats weighing 80–120 g were randomized into 2 groups, one receiving ad libitum 20% ethanol, the other water as drinking fluid. Each group has been divided in series of 8 to 12 rats which received 4 different diets combining different ratios of casein and fats. The experiments lasted from 2 to 21 months. Trypsinogen, amylase, lipase, protein and DNA were measured at the end of the experiment. The action of ethanol is closely related to the dietary ratio of proteins and lipids: (1) With a 17–18.5% protein intake and a 10% lipid diet, amylase and chrymotrypsinogen are significantly reduced, but with a 35% fat diet, amylase, trypsinogen and chymotrypsinogen are increased as well as, very probably, the enzyme concentration in the zymogen granules. This increased concentration might explain the toxic action of ethanol in man, facilitating precipitation of protein plugs in the ducts, found in the first stage of chronic alcoholic calcifying pancreatitis. (2) With a 5–6% protein diet, ethanol lowers moderately the pancreaticconcentration of these enzymes. With increased lipid ratios of the diet, the level of thepancreatic enzymes is reduced.