A review.Modern drug discovery is a highly complex and multi-disciplinary activity that began at the turn of the twentieth century, and structural biol. started to have an impact in the seventies.The first drug derived from a structure-based approach, the antihypertensive captopril, an angio-tensin-converting enzyme inhibitor, was approved in 1981, followed by dorzolamide, a carbonic anhydrase inhibitor used for the treatment of glaucoma, in 1995.Structural biol. has been fully integrated in the pharmaceutical industry drug discovery pipeline, and many companies use both high-throughput screening and fragment screening to identify starting points for their small-mol. R&D programs.Two important criteria for pursuing a drug target are its druggability and the possibility to design selective drugs that do not bind closely related proteins to avoid potential adverse effects.Cryo-electron microscopy will be a most useful complementary technique to answer biol. questions, mostly by addressing large and/or dynamic macromol. complexes and challenging targets such as membrane proteins.