One of two Ca antagonists, benidipine (3-30 microg/kg) or nifedipine (30-600 g/kg), was administered in a bolus injection through the jugular vein, and the changes in mean arterial pressure (MAP), renal flow (RF), and hindquarter flow (HQF) in conscious spontaneously hypertensive rats (SHRs) and normotensive control rats (NCRs). Renal vascular resistance (RR) and hindquarter resistance (HQR) were calculated as MAP divided by RF and HQF, respectively. When a high dose was administered to decrease the blood pressure by about 20%, the RR was significantly lower with benidipine than with nifedipine. The decrease in HQR was not significantly different between benidipine and nifedipine. When a low dose was administered to decrease the blood pressure by about 7%, the decrease in RR was not significantly different between benidipine and nifedipine, but the HQR was significantly lower with benidipine than with nifedipine. In the NCRs, no pharmacological properties were significantly different between these two Ca antagonists.