A hypercoagulable state might contribute to increased atherothrombotic risk in hypertension. The sympathetic nervous system is hyperactive in hypertension, and it regulates hemostatic function. We investigated the effect of non-specific -adrenergic stimulation (isoproterenol) and blockade (propranolol) on clotting diathesis in hypertension. Fifteen hypertensive and 21 normotensive subjects underwent isoproterenol infusion in two sequential fixed-order doses of 20 and then 40 ng/kg/min for 15 min/dose. Double-blind, 13 subjects were studied once receiving placebo and once receiving propranolol (100 mg/d) for 5 days each. In hypertensive subjects, isoproterenol elicited a dose-dependent increase in plasma von Willebrand factor (vWF) antigen (F_2,34= 5.02, p=.032), and a decrease in D-dimer (F_2,34= 4.57, p=.040), whereas soluble tissue factor (TF) remained unchanged. Propranolol completely abolished the increase in vWF elicited by isoproterenol (F_1,12= 10.25, p=.008) but had no significant effect on TF and on D-dimer. In hypertension, vWF is readily released from endothelial cells by -adrenergic stimulation, which might contribute to increased cardiovascular risk. However, -adrenergic stimulation alone may not be sufficient to trigger fibrin formation in vivo.