Six normal volunteers were studied on four separate occasions. On each occasion they received two concomitant infusions which were either placebo/placebo, placebo/tyramine, angiotensin II/placebo or angiotensin II/tyramine. Angiotensin II infusion was given at a constant rate of 2ng/kg/min whereas the tyramine infusion consisted of 10 min increments at 1.25, 2.5, 3.75, 5, 7.5 and 10 micrograms.kg-1.min-1. Tyramine infusion caused a dose dependent increase in systolic blood pressure with increases in diastolic blood pressure and plasma noradrenaline only at the highest doses. These changes were not affected by concomitant angiotensin infusion. We have therefore found no evidence to support the enhancement of haemodynamic or plasma noradrenaline responses to tyramine infusion by low dose infusion of angiotensin II in man.