Because of the central role of Ras in cancer cell signaling, there has been considerable interest in developing small molecule inhibitors of the Ras signaling pathways as potential chemotherapeutic agents. This chapter describes the use of a two-hybrid approach to identify the MCP compounds, small molecules that disrupt the interaction between Ras and its effector Raf. We first outline the reagent development and selection/counter selection methods required to successfully apply a two-hybrid approach to isolation of MCP compounds. Separately, we describe the collateral benefits of this screening approach in yielding novel antifungal compounds. We then discuss secondary physiological validation approaches to confirm the MCP compounds specifically target Ras-Raf signaling. Finally, we develop a decision tree for subsequent preclinical characterization and optimization of this class of pathway-targeted reagent.