Impaired exocrine pancreatic secretion has been frequently observed in diabetic patients by different methods, including direct function tests. However, the clinical importance remained unclear. In the present study, the fecal fat excretion in patients with type 1 or type 2 diabetes mellitus and exocrine dysfunction according to fecal elastase 1 concentrations <100 microg/g was investigated. Subjects with a history of gastrointestinal cancer, gastrointestinal surgery, alcohol abuse, or inflammatory diseases were excluded. In 101 patients the mean (+/- SD) fat excretion was 9.19 +/- 5.39 g. Only 41 patients (40.6%) had normal fat excretion <7 g/day. In 40 patients (39.6%), it was higher than 10 g/day, indicating relevant steatorrhea. The fat excretion did not correlate with diabetes type, duration, or clinical symptoms. This finding is of some clinical importance and might influence pathophysiological concepts and the management of diabetic patients.