The intersection of chemistry and pharmacology is called medicinal chemistry. This discipline is concerned with the designing, development and chemical synthesis of pharmaceutical drugs. It focuses on the identification and synthetic alteration of new chemical entities in order to make them appropriate for therapeutic use. Medicinal chemistry also studies the existing drugs and agents and their structure-activity relationships. The discovery of pharmaceutical drugs involves the assay of compounds for carrying out any desired biological activity. This happens through repurposing existing pharmaceutical agents towards any new pathologic process. Structural analysis in medicinal chemistry focuses on assessing the structure of pharmaceuticals. It helps in predicting their stability, efficacy and accessibility. This book brings forth some of the most innovative concepts and elucidates the unexplored aspects of this discipline. Different approaches, evaluations, methodologies and advanced studies on medicinal chemistry have been included herein. In this book, using case studies and examples, constant effort has been made to make the understanding of the difficult concepts of this field, as easy and informative as possible, for the readers.