The aim of this study was to determine whether chronic hyperinsulinemia, comparable to that found in obesity-associated hypertension, causes sustained increases in mean arterial pressure (MAP) or potentiates the hypertensive effects of angiotensin II (ANG II). Insulin infusion (0.5 or 1.0 mU/kg/min, IV), with plasma glucose held constant by IV glucose infusion, for seven to 28 days raised plasma insulin by five- to ten-fold, but did not significantly change MAP in dogs with reduced kidney mass that were maintained on high sodium intake. In dogs infused with ANG II to cause mild hypertension, insulin for 28 days did not potentiate the hypertension. Insulin infusion did, however, cause modest sodium retention during the first few days of infusion. These findings suggest that additional factors besides hyperinsulinemia per se are responsible for obesity-associated hypertension.