In order to study if the vasodilatory action of insulin is impaired in essential hypertension, 24 untreated patients were challenged with a 2 h euglycaemic hyperinsulinaemic clamp (56 E/m2). Cardiac index (CI) was measured by thoracic impedance cardiography and leg blood flow (LBF) by Doppler ultrasound. During the clamp procedure a significant decline in blood pressure was seen (3.0-5.6% over 120 min, P < 0.001). However, no significant effects on ejection fraction (+6 +/- 8 s.d.%), CI (-1 +/- 2%), heart rate (+2 +/- 1%) or total peripheral resistance (TPRI, -0.5 +/- 2%) were found. LBF increased by 22 +/- 35% (P < 0.005). These haemodynamic effects of insulin were not related to age, sex, body mass index, blood pressure or the insulin-mediated glucose uptake during the clamp. In conclusion, insulin increased LBF, but no changes in CI and TPRI were seen in the hypertensive patients. Furthermore, no association between the ability of insulin to induce vasodilatation and to promote glucose uptake was seen.