Drug discovery is usually a long and arduous process. However, pharmaceutical industries are making a significant progress in simplifying certain aspects of drug discovery process, especially in the area of target discovery, validation, and lead‐compounds discovery. Advances in recombinant DNA technology are intimately connected with the explosion of newly identified pharmaceutically important targets, and an understanding of how these targets function to regulate biological processes of interest. This is providing new and exciting opportunities for therapeutic intervention in diseases including those diseases that were thought to be untreatable a few years back. In this chapter we describe how each stage of drug discovery, from target identification to lead generation and even clinical trials, have benefited from the tools of recombinant DNA technology.