This document discusses cancer immunotherapy. It begins by describing tumor antigens that can be recognized by the immune system, such as tumor-specific antigens, tumor-associated antigens, and antigens from oncogenic viruses. It then discusses how tumors evade the immune system and various approaches to immunotherapy, including active immunotherapies using vaccines made of tumor cells, purified antigens, or antigen-loaded dendritic cells. Passive immunotherapies discussed include adoptive cellular therapy, monoclonal antibodies, and immunotoxins. Clinical trials and effectiveness of different immunotherapies are also summarized.