A pharmacological inhibition of nitric oxide synthase (NOS) in rats produces vasoconstriction, renal dysfunction, and hypertension. The present study was aimed at investigating whether the methanol extract of Serous commixta cortex (MSC) ameliorates $N^G$-nitro-L-arginine methylester (L-NAME) induced hypertension in rats. Treatment of rats with L-NAME (10 mg/kg/day in drinking water, 5 weeks) caused a sustained increase in systolic blood pressure (SBP). Administration of MSC (100 or 200 mg/kg/day, p.o) significantly lowered the SBP in the L-NAME-treated rats and this effect was maintained throughout the whole experimental period. Moreover, ecNOS expression in aorta and kidney tissue from L-NAME treated rats was significantly restored dy administration of MSC. Furthermore, the impairment of acetylcholine (ACh)-induced relaxation of aortic rings in the L-NAME treated rats was reversed dy administering of MSC. The renal functional parameters including urinary volume, sodium excretion, and creatinine clearance (Ccr) were also restored by administering MSC. Taken together, the present study suggeststhat MSC prevents the increase in SBP in rats with L-NAME-induced hypertension, which may result from the up-regulation of the vascular and renal ecNOS/No system.