Abstract A multistage exercise test was carried out in normotensive subjects with normotensive parents (controls; n = 12), and 32 offspring of essential hypertensive patients that were normotensive (NTO; n = 20) or bordeerline hypertensive (BHO; n = 12) The groups were comparable as to age, weight and working capacity. Changes in sympathetic nervous activity were determined by measurements of plasma noradrenaline. The initial rise in noradrenaline levels during the exercise test was proportional to the increase in work load until the noradrenaline concentration rose sharply to levels more than 1000 pg/ml above baseline levels. The work load immediately prior to the steep rise in plasma noradrenaline (sympathetic threshold level: STL) is considered to represent the point from which anaerobic energy-yielding processes play an increasingly greater role as the work load increases. The initial increase in plasma noradrenaline until STL was significantly higher in both the NTO (p < 0.02) and BHO (p < 0.005) compared to the control group. The absolute noradrenaline level at STL and the increase in noradrenaline from baseline to STL were significantly higher in the BHO group (p < 0.02, p < 0.005). No significant differences between the groups were found when comparing noradrenaline levels at rest or at absolute or relative work loads. The systolic blood pressure response during the exercise test was significantly more pronounced in the BHO group (p < 0.05) compared to the controls and the NTO group.