Patients with advanced head and neck cancer have significant reduction in their circulating lymphocyte mass which is reflected in decreased numbers of T cells, Fc receptor cells, and in derangements of T lymphocyte functions, i.e., decreased responsiveness to several dilutions of phytohemagglutinin and lack of development of delayed hypersensitivity to 2,4-dinitrochlorobenzene (70% of patients were DNCB (-)). A population of phagocytic cells capable of decreasing lymphocyte responsiveness to mitogens were demonstrated. Removal of these cells resulted in an increment in lymphocyte responsiveness. Immunological impairment seemed to correlate with patients' ability to become sensitized to DNCB. Those patients who were DNCB (+) had less derangement in their immunological parameters. Weekly administration of Corynebacterium parvum in conjunction with chemotherapy did not have a discernible effect on patient's immune reactivity.