In this chapter, we provide an overview of nitric oxide (NO)-tyrosine phosphorylation signal transduction pathways, integrating them with the cyclic guanosine monophosphate (cGMP) and S-nitrosylation-mediated pathways that are triggered by NO. The second half of this chapter includes a description of the methods that our laboratory has used extensively to characterize the mechanisms involved in signaling events mediated by this pathway. These include assays for detecting protein tyrosine phosphorylation, tyrosine phosphorylation of the epidermal growth factor (EGF) receptor, phosphorylation of the ERK1/2 mitogen-activated protein (MAP) kinases, transfection of cells with modified forms of p21Ras, and an assay of p21Ras.