To evaluate the reactivity to psychological stress in patients with essential hypertension we investigated hemodynamic and endocrinologic changes during a mental arithmetic task (MAT) and a mirror drawing test (MDT) in 10 hypertensive subjects. Hemodynamic changes were assessed continuously using an ambulatory radionuclide cardiac detector. There were significant increases in systolic blood pressure (deltaSBP: +37.8 +/- 11.1 and +41.0 +/- 9.4 mm Hg during MAT and MDT, respectively, P < .01) and diastolic blood pressure (deltaDBP: +17.5 +/- 3.1 and +21.2 +/- 3.9 mm Hg, P < .01) and in heart rate (deltaHR: +17.1 +/- 5.3 and +12.5 +/- 2.9 beats/min, P < .01) during both tasks in association with an increase in cardiac output (CO). The plasma levels of norepinephrine and epinephrine increased during both the MAT (deltaNE: +0.074 +/- 0.022 ng/mL, P < .01; deltaEP: +0.068 +/- 0.025 ng/mL, P < .01) and the MDT (deltaNE: +0.067 +/- 0.034 ng/mL, P < .01; deltaEP: +0.030 +/- 0.011 ng/mL, .05 < P < .1). Although the deltaNE was similar in response to the MAT and MDT, the deltaEP during the MDT tended to be less than half the deltaEP during the MAT (.05 < P < .10). The deltaEP was positively correlated with the deltaDBP and the deltaCO during both tasks and with the deltaSBP and the deltaHR during the MAT. These findings suggest that MAT- and MDT-induced increases in BP were attributable mainly to an increase in CO, possibly as the result of stimulation of the sympathoadrenomedullary system. However, the sympathoadrenomedullary system appeared to be more closely associated with the hemodynamic responses during the MAT than during the MDT.