We studied the functional response and phenotypic characterization of peripheral blood T cells and their correlation with the clinical stage of disease in 29 males with previously untreated carcinoma of the larynx and 24 healthy male controls. Peripheral blood T cells, phenotypically CD2+ CD3+, were significantly decreased in the patients relative to the controls. Patients with advanced locoregional extension (T4 and N1, 2, 3) also showed a diminution of the CD4+ subpopulation of T cells. DNA synthesis by purified T cells showed similar blastogenic responses in patients and controls; the interleukin-2 production of phytohemagglutinin stimulated lymphocytes was also normal. We conclude that in patients with laryngeal carcinoma there is a phenotypic alteration of the T cells that is variable according to tumor stage, without functional alterations in blastogenic capacity or IL-2 production.