This famous textbook was conceived in the early 1970s by two of the renowned Indian educators and professors of Microbiology. The first edition, published in 1978, was a masterpiece of clarity and uniformity of style. Although the format and presentation have seen many changes in the eight subsequent editions, the authors' original vision and objectives remain. More than three and a half decades after its first publication, the book continues to inform and educate students and teachers. The ninth edition has been completely updated and revised. In accordance with advances in the field, the sections on Immunology, Mycology and Clinical Microbiology have been given due prominence. To better prepare students for clinical situations, case studies, approach to treating common diseases and algorithms and flowcharts have been included. Practice questions that mirror those that frequently appear in examinations have been provided at the end of every chapter. The presentation and layout has been tailored to help students absorb information quickly, as greater demands are placed on their time. Illustrations and photographs have been improved to enable ease of learning and retention of information.