This book fuses heterocyclic chemistry and drug discovery two areas that have gone hand-in-hand in the practice of medicinal chemistry, but have not yet come together for training novice medicinal chemists and students. Rather than leave these groups to learn on the job, this book brings together the collective 100+ years of drug discovery experience from academic and industry contributors to provide a valuable guide to the role and application of heterocyclic chemistry for pharmaceuticals. The chapters use a plethora of case studies to illustrate the role of the main classes of heterocycles (3, 4, 5, 6 + ring systems) in drug discovery.