This book integrates various scientific disciplines, including biology, toxicology, pharmacology, theoretical chemistry, microbiology and biopharmacy within the field of medicinal chemistry, which is an exciting and dynamic field that plays a crucial role in drug discovery and development. This book is the result of 30 years of teaching and engaging with graduate students across multiple universities. The encouragement from faculty and students for the earlier works has motivated the authors to present the second edition of the popular book. Designed as a comprehensive yet accessible resource, this book follows the latest syllabus set forth by the Pharmacy Council of India, catering specifically to undergraduate students preparing for Medicinal Chemistry I. This volume comprises twelve chapters covering essential topics such as the history and development of medicinal chemistry, physicochemical properties, metabolism, and various classes of drugs, including adrenergic, cholinergic, sedatives, antipsychotics, anticonvulsants, narcotics, and anti-inflammatory agents. Each chapter provides a clear introduction, classification with examples, structure?activity relationships (SAR), detailed information on individual drugs including structure, IUPAC names, mechanisms of action, uses, and selected synthesis to facilitate student understanding.