The book spread over 17 chapters covers the mechanisms of innate and specific immunity along with latest developments in vaccination and disease control using immunological tools. The complex mechanisms have been explained in a simplified way using line diagrams, figures and tables, so that they are readily understood. Another feature of the book is that, wherever considered appropriate, aspects of human or animal immunology have been narrated for comparison. We hope that we have been able to transmit the exCitement of the remarkable insights gained into the subce1lular/biomolecular mechanisms of defence in fish and shellfish to the readers. As such the book may serve as a good reference for both undergraduate and postgraduate students of fisheries, aquaculture, zoology and life science disciplines for gaining a preliminary knowledge on immune mechanisms of tish and shellfish.