In a previous study, mild to moderate exocrine pancreatic insufficiency, as measured by the secretin-pancreozymin test, was found in 23 (43%) of 53 patients with type-1 diabetes mellitus. Of these 53 patients, 20 (7 of whom initially had an abnormal secretin-pancreozymin test) were available for a follow-up examination 11 years later. Of the 7 patients with abnormal exocrine pancreatic function at the first test, 5 remained abnormal and 2 became normal, whereas of the 13 patients with initially normal pancreatic function the test result remained normal in 11 patients and became abnormal in 2. In these 2 groups the test result did not differ significantly between both tests. However, exocrine pancreatic function had returned to normal or had become abnormal in 2 patients, respectively, at the second test. In the 3 patients with exocrine pancreatic insufficiency at the first and second tests, the lipase level had not fallen below 10% or less than the normal level at which steatorrhea occurs and therapy is required. There was no significant correlation between the duration of the diabetes and the test results for both time points of investigation. The data suggest that mild to moderate exocrine pancreatic insufficiency found in type-1 diabetes is due to an early event in the course of the diabetes and does not progress. Therefore, this finding is of minor clinical importance and expensive pancreatic enzyme substitution will not be required.