Gasotransmitters, such as nitric oxide, carbon monoxide and hydrogen sulfide, can be generated endogenously. These gasotransmitters play important roles in vascular biology, including vasorelaxation and inhibition of vascular smooth muscle cell (VSMC) proliferation. In recent years, sulfur dioxide (SO2) has been considered as the fourth gasotransmitter. SO2 is present in air pollution. Moreover, SO2 toxicity, including oxidative stress and DNA damage, has been extensively reported in previous studies. Recent studies have shown that SO2 can be endogenously generated in various organs and vascular tissues, where it regulates vascular tone, vascular smooth cell proliferation and collagen synthesis. SO2 can decrease blood pressure in rats, inhibit smooth muscle cell proliferation and collagen accumulation and promote collagen degradation, and improve vascular remodelling. SO2 can decrease cardiovascular atherosclerotic plaques by enhancing the antioxidant effect and upregulating nitric oxide/nitric oxide synthase and hydrogen sulfide/ cystathionine-gamma-lyase pathways. SO2 can also ameliorate vascular calcification via the transforming growth factor - beta 1/Smad pathway. The effect of SO2 on vascular regulation has attracted great interest. SO2 may be a novel mediator in vascular biology