The compelling demand of the tenth edition of this book is convincing proof that Dr. Allen left an indestructible monument of homeopathic materia medica, one that is true to Homeopathy and immensely helpful to every physician who consults it. Keynote symptoms of a drug convey its ?fundamental or central idea?. They also help in making quick, confident, effective and most practical prescriptions. This book will assist students in understanding and applying Materia Medica quickly and with efficiency. The book aims to present the outline and the leading characteristics of the drugs which help a student in selecting the similimum. As stated by Dr. Hahnemann, the most peculiar, singular and distinguishing symptoms lead the physician to the right remedy. Besides such red-line symptoms, the inclusion of a repertorial index makes this book an essential mate for both students at undergraduate, post graduate and competitive levels and practitioners alike. Interesting Fact- Allen?s keynotes book is entirely based on Hering's Guiding Symptoms. For each drug, Allen selected some symptoms from "Guiding Symptoms'' according to his sense of priority and his own personal experience. The remedy relationships in Allen's "Keynotes' ' are also based entirely on Hering`s Guiding symptoms. While the term `keynote` was coined by Dr. Guernsey, the real ?Keynote system? is strictly Hahnemannian. Additionally, the section on the indications of Bowel nosodes medicines by John Paterson are mentioned at the end of the book making it a complete materia medica package.