Type 2 diabetic patients are known to frequently have a high insulin level and were recently described as having high plasminogen activator inhibitor (PAI) activity, compared to normal controls. As we have shown in several clinical conditions (normal subjects, obese patients, angina pectoris patients) that plasma PAI activity was linked with plasma insulin, we have studied in 38 type 2 diabetic patients the relationship between PAI activity, insulin and other parameters. Patients showed higher level of PAI activity, as well as plasma glucose, insulin, triglyceride, cholesterol and Apolipoprotein B levels than normal controls; highest values were observed with diabetic patients also affected by coronary artery disease. A significant correlation was found between PAI activity and insulin (r = 0.60, p less than 0.001), body mass index (r = 0.32, p less than 0.05) and Apolipoprotein B (r = 0.33, p less than 0.05). The two latter correlations disappeared after adjustment for insulin. These results are in agreement with our previous report showing an in vitro effect of insulin on the synthesis of PAI by a hepatocellular cell line. Hyperinsulinemia presented by type 2 diabetic patients may increase the hepatic synthesis of PAI, inducing an hypofibrinolysis, which could play a role in the development of the vascular complications. Attempts to reduce hyperinsulinemia could have a favorable effect by lowering PAI activity.