Although pancreatic exocrine enzymes are often elevated in patients with fulminant type 1 diabetes, the onset of this elevation and its significance in disease development remain unclear. We therefore investigated the significance of elevated serum enzyme concentrations and pancreatic swelling in the development of fulminant type 1 diabetes. Serum pancreatic exocrine enzymes, including amylase, elastase-I, lipase and trypsin, were measured during the course of the disease in 11 patients with fulminant type 1 diabetes (3 men and 8 women; a range of age 24-73 years, median 33 years; a range of HbA1c at onset 4.5-6.7%, median 6.0%), all of whom developed ketotic diabetes requiring intensive insulin therapy within a month. At least one pancreatic exocrine enzyme was elevated in each patient during the course of the disease. The concentration of enzymes on admission could not be correlated with urinary excretion of C-peptide. The time course of increase in serum amylase varied in these patients. In conclusion, neither the level of serum amylase nor the swelling of pancreas was associated with the onset or severity of fulminant type 1 diabetes. The pancreatic exocrine and endocrine events may occur concomitantly but independently during the course of fulminant type 1 diabetes.