The present study was carried out to investigate the effect of water extract and 70% ethanol extract from Gastrodiae Rhizoma on cardiovascular activities and plasma levels of catecholamines in unanaesthetized spontaneously hypertensive rats. The depressor response in SHR was observed during three to six hour period after an oral administration of water extract from Gastrodiae Rhizoma(GR). There was a statistically significant correlation between the magnitude of the depressor response induced by an oral administration of water extract from GR and the initial control blood pressure level. The increase in blood pressure induced by norepinephrine was less in Wistar rat treated with GR water extract than those without GR extract. No significant change in heart rate was observed in SHR receiving either water extract or ethanol extract from GR. Associated with the depressor response, there was a concomitant reduction in plasma levels of norepinephrine in SHR at 4 hour after an oral administration of water extract from GR. Plasma levels of norepinephrine and epinephrine were decreased slightly at 2 hour after an oral administration of ethanol extract from GR. These results suggest that the depressor effect of water extract from GR may be due, in part, to a decreased sympathoadrenal activity.