Immunology, in all its facets of immunochemistry, humoral immunity, cellular immunity, immunodiagnosis, and immunotherapy, is currently the most rapidly advancing discipline of clinical and experimental oncology. But as in most developing subjects, it is continually beset with problems of methodology and nomenclature, both of which are often intertwined. Indicative of this problem are our circular definitions of antigen and antibody. Another fre quent problem is the use of the words "specific" and "associated" when characterizing re actions to tumors or the antigenic properties of neoplasms....