Fibrinolytic activity is primarily determined by the balance between the levels of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1).1 Impaired fibrinolytic function, characterized by increased PAI-1 level and decreased t-PA activity, has been found in patients with hypertension. The t-PA antigen concentration reflects both active t-PA and inactive t-PA complexed with PAI-1. The t-PA antigen concentration is determined in part by increased PAI-1 level. Free and unbound t-PA is physiologically active and leads to endogenous fibrinolysis.