Hydrogen sulfide (H(2)S) may be endogenously produced by cystathionine beta-lyase (CBS) and cystathionine gamma-lyase (CSE) as a cardiovascular physiological functional factor. On the hypoxic pulmonary hypertension (HPH) animal model, the plasma H(2)S concentration, the gene expression and the activity (CSE) were decreased in lung tissues In L-NAME induced hypertension and spontaneous hypertension rats (SHR) models, the plasma H(2)S concentration, vascular CSE activity and mRNA expression were obviously decreased. When H(2)S was exogenously supplied, systolic pressure obviously decrease. These studies suggested that CSE/H(2)S pathway participated in the pathophysiological development of hypertension. The endogenous level of H(2)S produced by some arterial tissues increased in both septic and endotoxic shock rats. The level of H(2)S highly correlated with the endogenous level of NO. These results suggest that H(2)S may be a novel cardiovascular functional regulator.