SUMMARY The bemodynamic response to mental stress (mental arithmetic) was studied in adolescents with varying risk factors for essential hypertension (EH). One group (genetic) consisted of nonnotensive well adolescents who had at least one parent with EH. Another group (labile) consisted of adolescents with labile hypertension each of whom also had at least one parent with EH. The control population consisted of normotensive adolescents with a negative family history of EH. Subjects with labile hypertension demonstrated a sustained increase in systolic and diastolic pressure and heart rate during stress. This response was significantly different than the control population (p < 0.001). The stress response of the nonnotensive genetic population was qualitatively similar to the group with labile hypertension and significantly different than the controls in diastolic pressure and heart rate (p < 0.001, < 0.02). Post-stress plasma catecholamines were higher in the labile hypertensive and genetic groups than in the control group. These findings demonstrate increased central nervous system mediated adrenergic activity and cardiovascular response in labile hypertension and also in some normotensive subjects with a genetic risk for hypertension.