Although historically known as toxic gases, H₂S and NO are currently well recognized as endogenous signaling molecules, namely gasotransmitters, in mammalian systems. More interestingly, a plethora of research in the past decade has revealed the interaction between these two molecules by either regulation of mutual biosynthesis or direct chemical reaction. This helps explain their functional similarity and mutual potentiation, particularly in the cardiovascular system. This chapter serves as a general overview on the biochemistry of interaction of H₂S and NO and how this interaction occurs in the context of the cardiovascular system, cancer biology, and inflammation. Moreover, recent synthesized NOSH compounds, which simultaneously donate NO and H₂S, are briefly summarized in this chapter.