Hydrogen sulfide (H(2)S) is a newly found modulator in vascular system. This work showed that gene expression of cystathionine gamma-lyase (CSE), a H(2)S generating enzyme, and the activity of CSE in thoracic aorta were suppressed in hypertension rats. The plasma level of H(2)S also decreased in those rats. Exogenous administration of H(2)S could increase the plasma level of H(2)S and enhance the CSE activity of aorta. Exogenous administration of H(2)S also attenuated the elevation of pressure and lessened the aorta structural remodeling during the development of hypertension. In WKY rats, the gene expression and activity of CSE also decreased when the endogenous production of H(2)S was deprived by administration of DL-propargylglycine (specific inhibitor of CSE), accompanying the elevated pressure and the development of vascular remodeling. The results showed that endogenous H(2)S system was involved in both the maintenance of basal blood pressure and the development of hypertension. Exogenous H(2)S could exert beneficial effect on the pathogenesis of spontaneous hypertension.