The aim of this study was to evaluate the fibrinolytic system by measurement of fibrinogen, plasminogen, tissue-type plasminogen activator (t-PA), and plasminogen activator inhibitor-1 (PAI-1) in healthy normotensive subjects and in patients with essential hypertension. A group of 21 healthy normotensive subjects [age, 39.2 +/- 1.8 years; 8 males, 13 females; body mass index (BMI) = 27.9 kg/m] and 42 patients with untreated essential hypertension (age, 47.6 +/- 1.7 years; 19 males, 23 females; BMI = 28.3 kg/m) were studied. Blood samples and clinical measurement were taken between 7 am and 9 am by an observer in a blind fashion. The systolic/diastolic blood pressure of normotensive subjects was 121.3 +/- 2.5/78.4 +/- 1.3 mm Hg and that of hypertensive patients was 166.4 +/- 4.3/102.9 +/- 1.83 mm Hg, measured in the sitting position. Plasma fibrinogen levels in the normotensive and hypertensive individuals were 295.7 +/- 9.4 mg/dL and 305.67 +/- 10.9 mg/dL, respectively (P = 0.456). The corresponding values for plasminogen were 71.4 +/- 3.8% and 89.5 +/- 2.5%, (P = 0.0031), for t-PA were 6.3 +/- 0.5 ng/mL and 7.6 +/- 0.4 ng/mL (P = 0.0487), and for PAI-1 were 46.9 +/- 5.1 ng/mL and 63.0 +/- 5.6 ng/mL (P = 0.0324), respectively. In conclusion, patients with essential hypertension have disequilibrium in the fibrinolytic system with a tendency toward a hypercoagulability state when compared with normotensive subjects. This state could explain, in part, the thrombotic complications that occur with a higher frequency in hypertensive patients as compared with normotensive subjects.