Immunology is one of the applied subjects because of its importance in clinical field. The study of our immune system helps to keeb the body in a better working condition and disease free life. This book covers the syllabus of “Immunology” paper for both B.Sc. and M. Sc. Zoology prescribed by Many Universities. This book attempts to present a simple, understandable text with diagrams. This book contains 20 Chapters. They includes topics related to Immunity, lymphoid organs, antigens, vaccines, antibody, complements, major histocompatibility complex, immune response to diseases, tumour therapy, Immune deficiency diseases, autoimmune diseases and hypersensitivity. The text is presented in a very readable way and concise description of information is easy-to-follow the immune response by medical and graduate students. Student can understand each topic with elaborate well-illustrated diagram and a valuable reference book for the experienced teacher. I tried my best to make this book interesting and readable. This book also helps the readers to easily learn about essential of immunology. It Includes the glossary and question information on the topics discussed.