This study was done to investigate the effect of Gamisamool-tang(GMSMT) on hypertension. After administering GMSMT extract to SHR for 5 weeks, changes in blood pressure, pulse rate, aldosterone and catecholamine levels in plasma were examined, and immunohistochemical changes were observed, and liver function test was done. The following results were obtained; blood presure decreased significantly as well as levels of aldosterone, norepinephrine and epinephrine in SHR, But levels of dopamine were unaffected. No capillary vessel dilation in adrenal cortex was observed. Safety against hepatic toxicity was showed. These results support a role for GMSMT might be usefully applied in treatment of hypertension.