The authors examined 25 patients with diabetes mellitus type 2 (NIDDM) without vascular complications, treated by sulphonyl urea preparations, 12 hyperinsulinaemic (HI) non-diabetic subjects and 11 normoinsulinaemic healthy subject s. Patients with NIDDM and HI non-diabetics had significantly elevated PAI-1 levels which correlated with the C-peptide level (r = 0.519, p < 0.001), triacylglycerols (TG) (r = 0.685, p < 0.001), BMI (r = 0.607, p < 0.001) and levels of endothelial markers such as von Willebrand s factor and thrombomodulin (TM). In the group of patients with NIDDM no relationship of PAI-1 and C-peptide was found and a significant correlation was found with TM levels (r = 0.609, p = 0.001) and TG levels (r = 0.476, p = 0.046). The results suggest that the endothelial department has an effect on the regulation of PAI-1 levels in patients with NIDDM.