The authors report the case of a 37-year-old female complaining of chronic diarrhea since childhood. She had gross steatorrhea and azotorrhea . Pancreatic function tests using secretin and cholecystokinin-pancreozymin stimulation, and analysis of pure pancreatic juice collected under secretin stimulation proved exocrine pancreatic insufficiency. Oral glucose tolerance test was normal. Intestinal absorption tests, small bowel X-ray films and jejunal histology were normal. Brush-border specific enzyme activities were increased. In vitro palmitic acid uptake and esterification in the jejunal mucosa were decreased. There was no pancreatic calcification. Biliary tract was normal. Retrograde pancreatography, pancreatic ultrasonography and tomodensitometry showed no morphologic abnormality. No cause of exocrine pancreatic insufficiency could be detected. A son and a niece of the proband had chronic diarrhea and growth failure. The relationship of the described case with primary lipomatosis of the pancreas in childhood and hereditary exocrine pancreatic insufficiency in CBA/J epi mice is discussed.