of tumor immunol­ ogy addresses the nature and uniqueness of tumor-associated antigens in humans, the identification of the stages of differentiation and functions of the various cell types involved in immunity is advancing rapidly. The de­ velopment of monoclonal antibody methodologies, together with progress in the biochemical characterization of cell markers, cell separation, and measurement of cell functions, has significantly aided in the identification and quantitation of different cell types. Establishing the role of these cells in the regulation of human immune mechanisms offers a means for evalu­ ating the status of the immune responses in cancer patients and for assessing the effects that tumor and antitumor treatments may exert on their func­ tionality, which, in turn, may alter the effects of antitumor treatments.