The change of blood pressure and heart rate after intravenous injection of Korea red ginseng (KRG) were studied in the conscious normotensive and one-kidney, one-clip Goldblatt hypertensive (1K, 1C-GBH) rats. Crude saponin (CS) of KRG (50, 100 mg/kg i.v.) induced a hypotensive effect and bradycardia in a dose-dependent manner in the anesthetized rats. On the other hand, CS of KRG (100 mg/kg) induced a hypotensive effect and reflex tachycardia in the conscious rats. Saponin-free fraction (SFF) of KRG did not affect them in the anesthetized normotensive rats (P>.05). The maximal hypotensive effect by CS of KRG in the conscious 1K, 1C-GBH hypertensive rats and L-nitroarginine methyl ester (L-NAME, 40 mg/kg)-treated conscious hypertensive rats was not different from that of conscious normotensive rats (Delta 31.6+/-6.3, Delta 27.5+/-5.8 vs. Delta 26.7+/-4.3 mmHg, P>.05). However, pretreatment of L-NAME significantly inhibited the reflex tachycardia by CS of KRG (70.8+/-7.0 vs. 30.6+/-15.0 bpm, P<.05). Hemolysate-sensitive nitric oxide (NO) current by the CS of KRG was greater than that of the SFF of KRG (651.9+/-128.2 pA for CS and 164.9+/-92.5 pA for SFF, P<.001). These findings suggest that KRG has a hypotensive effect and its effect may be due to saponin fraction of KRG in the conscious rats. The releasing effect of NO of KRG, like NO donor, may be partly contributed to the hypotensive effect of KRG.