This chapter describes various components of reactive nitrogen species (RNS) response networks and their associated regulatory circuitry. It focuses on how these components are used to identify additional regulatory components and elucidate RNS response networks as a function of RNS source and growth conditions. It summarizes the complementary nature of traditional biochemical analysis and systems-wide analysis in identification and characterization of the bacterial response to RNS. Bacteria have evolved complex regulatory networks for dealing with a variety of chemical stressors. The bacterial response to RNS is relevant to both pathogenesis and denitrification and thus has been extensively characterized. Traditional biochemical analysis has identified and characterized many of the key RNS response elements, such as flavohemoglobin hmpA and response regulator NorR. Additionally, systems-wide analysis aids in the identification of additional network components and determination of their contribution to the overall network behavior. These systems-wide analyses have led to the identification of response regulator NsrR, Fe-S cluster repair agent YtfE, and the critical NO target. The extensive body of knowledge regarding the bacterial RNS response and RNS chemistry makes the RNS response network an excellent example of the combined power of traditional biochemical analysis and systems-wide analysis.