To elucidate whether a difference exists in blood pressure (BP) elevation during isometric handgrip exercise (IHG) between essential hypertensives (EHT) and normotensives (NT), IHG was carried out in 12 NT and 46 EHT under constant sodium intake using a new instrument. The acute effects of propranolol and prazosin on IHG were also examined in EHT. The change in systolic BP (delta SBP) during IHG in EHT, delta SBP = 61 +/- 21 mmHg, was markedly greater than that in NT, delta SBP = 28 +/- 4 mmHg. Among EHT, delta BP increased with increasing severity of hypertension. Neither the changes in plasma norepinephrine nor in epinephrine during IHG showed significant differences between EHT and NT. The pressor response during IHG could not be suppressed by propranolol, but about 30% suppression of BP was observed during IHG with prazosin. It is concluded from these findings that EHT have an exaggerated BP response to IHG that is due to increased post-junctional alpha 1-adrenoceptors.