Cancer is a worldwide public health problem. Each year, 6 million people die from cancer and 8.1million new cases are diagnosed.Cancers, however, arise from the host's own tissues, and thus almost all the genes expressed by tumors are also expressed by normal tissues. Can the immune system attack "altered self" while sparing "self"? Another question is why the immune system would evolve to fight tumors? Nevertheless, immune recognition of cancers has now been well documented in humans. The main indicator of cancer is the uncontrolled growth and dispersion of cells as a result of abnormal changes to the genetic material contained in those cells. This book is an attempt to throw light on the basic immunology, the role of immune intervention in the prevention or treatment of human cancers and an insight into the recent advances in the field of tumour immunology.