Low-dose dopamine is commonly used for the management of acute renal failure because of its exclusively renal vasodilator effect which is mediated through two specific receptors. However, the experimental background of this role is controversial in man. Indeed, the available data come mainly from animal trials and uncontrolled studies in patients with left ventricular dysfunction who need other drugs to improve cardiac output. This work was aimed at investigating Doppler value in assessing the effects of low-dose dopamine infusion in healthy subjects. Heart rate, arterial blood pressure and RI were measured before, during (at 10, 20 and 30 minutes) and after low-dose dopamine infusion in 4 healthy volunteers. In all subjects the RI reduced significantly, returning to the initial values after drug infusion. Indeed, the average RI (0.648 +/- 0.015 before drug administration) decreased to 0.595 +/- 0.026 within 10 min of infusion and remained almost the same during the infusion (0.596 +/- 0.024 within 20 min of infusion, 0.585 +/- 0.032 within 30 min). Within 10 min of the end of infusion, the average RI returned to similar values to those measured before drug administration (0.643 +/- 0.02). Changes in heart rate and arterial blood pressure were not significant. Our results confirm the vasodilator role of low-dose dopamine to be free of systemic effects in healthy volunteers with no therapeutic support which would cause extrarenal decrease in peripheral vascular resistance.