AbstractTumor cells contain a variety of antigens, including tumor associated antigens. The tumor associated antigens can be clinically useful as marker's for detection of cancer and some may also mediate host resistance against tumor growth. Much emphasis has been placed on the detection of circulating tumor associated markers, with radioimmunoassays for carci‐noembryonic antigen (CEA) being extensively utilized.At present, CEA does not appear to be promising for initial detection of cancer, but may find an important place in the determination of prognosis and early detection of recurrent disease. Many cancer patients have depressed immunologic competence, yet they frequently have cell‐mediated immunity against tumor associated antigens. Several different immuno‐therapeutic strategies have been developed, to either augment the immunologic responsiveness of the patient or to specifically increase the immune reactivity against tumor associated transplantation antigens.