Structural biology is an integral part of the drug discovery process in the pharmaceutical industry. Two complementary methods dominate among the experimental techniques capable of providing detailed three-dimensional (3D) structural information of therapeutically relevant targets, most often with bound ligands: protein crystallography and solution-phase NMR spectroscopy. The structural information these techniques provide continues to grow in depth and breadth, impacting every step of drug discovery from lead identification to preclinical testing ( Fig. 12.1). Used together, protein crystallography and solution-phase NMR can significantly increase both the pace of discovery and the quality of the resulting compounds that are moved forward into development.The benefits to drug discovery of rapidly available, high-resolution 3D structural information provided by protein crystallography are well established [1,2]. While the technique's success depends on diffraction-quality protein crystals, significant advances in protein biochemistry and protein crystallization technologies have dramatically increased the number of targets amenable to structure determination by X-ray diffraction. Driven in large part by a number of worldwide structural genomics efforts underway in both academia and industry [3], these advances include robotic systems for cloning, expression, protein purification and crystallization [4]. In addition, continued hardware and software developments, both at synchrotron and in-house X-ray sources, have decreased the time of de novo structure solution from months to days, while co-crystal structures are routinely obtained within hours. Thus, once diffraction-quality crystals are obtained, structure determination is not a bottleneck in the discovery process. In fact, a number of drugs on the market were discovered in large part by routine use of structural information provided by protein crystallography [2, 5], a clear indication that this technique has become a driver of the design process and not a retrospective analysis tool.In academia, solution-phase NMR spectroscopy continues to develop as a technique for obtaining 3D structural information of macromolecules including target-ligand complexes. Recent advances have made NMR structural work possible 249 Fragment-based Approaches in Drug Discovery. Edited