Abstract A new member of the adrenomedullin family, adrenomedullin2, was identified in mammals. The effects of adrenomedullin2 on renal hemodynamics and urine formation were examined in rats. Intrarenal arterial infusion of adrenomedullin2 at rates of 30, 100 and 300 pmol/kg/min decreased blood pressure and increased heart rate in a dose-dependent fashion. Adrenomedullin2 infusion at 100 pmol/kg/min significantly increased renal blood flow and urine flow. At the higher infusion rate (300 pmol/kg/min), adrenomedullin2 significantly decreased urine flow. Continuous intrarenal infusion of adrenomedullin2 at 100 pmol/kg/min significantly increased renal blood flow from 6.7±0.5 to 8.8±0.5 ml/min and decreased renal vascular resistance from 16±1 to 11±1 mm Hg min/ml. Urine flow was significantly increased from 21.5±4.9 to 36.2±8.5 μl/min and urinary excretion of sodium was increased from 2.3±0.9 to 4.9±1.4 μEq/min. Blood pressure, heart rate and glomerular filtration rate did not change. Infusion of a similar dose of adrenomedullin also increased renal blood flow (6.8±0.4–8.8±0.6 ml/min), urine flow (25.4±3.2–42.8±9.4 μl/min) and urinary excretion of sodium (2.8±0.6–6.5±1.2 μEq/min), decreased renal vascular resistance (15±1–11±1 mm Hg min/ml) and did not alter glomerular filtration rate. Thus, the renal actions induced by adrenomedullin2 were similar to those of adrenomedullin. These data suggest that adrenomedullin2 may play an important role in the regulation of renal hemodynamics and urine formation.