The aim of this study was to assess the function of the fibrinolytic system at rest and in response to adrenergic stimulation in patients with stable essential hypertension as compared with normotensives. At rest, essential arterial hypertensives were characterized by increased levels of circulating tissue-plasminogen activator, associated with an increased activity of its specific inhibitor, the PAI-1. After stress, fibrinolytic response was impaired in essential arterial hypertensives despite a greater release of tissue plasminogen activator by endothelial cells. Therefore, the PAI-1 activity may be increased in essential arterial hypertensives not only at rest, but also after stress. This may represent a risk factor for hypertensive patients.