Impairment of fibrinolysis is supposed to contribute to CVD. In 38 hyperlipoproteinemic patients, known to be at risk for early CVD, fibrinolytic activity was measured before and after stimulation with DDAVP. A negative correlation was found between serum triglyceride levels and fibrinolytic activity, both before and after DDAVP. A subnormal activity was invariably found when serum triglyceride concentration was above 8 mmol/L. The defect can be attributed to low levels of extrinsic plasminogen activator. High cholesterol levels were not associated with impairment of fibrinolyis. Fibrinolytic activity and response to DDAVP were lowest in those patients with hypertriglyceridemia who also had a tendency to develop hyperchylomicronemia (type V/IV). The low fibrinolytic activity in this type of hyperlipoproteinemia cannot be explained by obesity. Factor VIII was higher than normal in most patients with hyperlipoproteinemia; the level increased after stimulation with DDAVP in every patient. This imbalance between coagulation and fibrinolysis might increase the risk of CVD. Chemicals/CAS: adrenalin, 51-43-4, 55-31-2, 6912-68-1; blood clotting factor 8, 9001-27-8; clofibrate, 637-07-0; desmopressin, 16679-58-6; Antigens; Argipressin, 113-79-1; Cholesterol, 57-88-5; Chylomicrons; Desmopressin, 16679-58-6; Factor VIII, 9001-27-8; Plasminogen Activators, EC 3.4.21.-; Serum Globulins; Triglycerides