Rapid increase in information in medical sciences requires that textbooks be revised and updated to keep pace with the current trends. The seventh edition of the book is an updated version and elegantly meets the new course requirements of undergraduate medical students. The text has been thoroughly revised as per the Competency Based Undergraduate Curriculum for the Indian Medical Graduate. However, for the ease of learning and teaching traditional organism-based subject, brief description has been retained. Description of clinical case-based exercises, monkey pox and SARS-CoV-2 virus has been added.