We compared the phenotype and antitumor effector function of lymphocytes obtained from tumor tissues, lymph nodes, and the peripheral blood of patients with head and neck cancer. Freshly isolated tumor-infiltrating lymphocytes were deficient in CD4+ T cells in comparison with lymph node lymphocytes (LNL) and peripheral blood lymphocytes. A significantly higher CD4/CD8 ratio observed in LNL vs tumor-infiltrating lymphocytes and peripheral blood lymphocytes was attributable to both a significant enrichment in CD4+ T cells as well as a decrease in CD8+ T cells. The percentage of natural killer cells (CD3-CD56+) was uniformly low in both tumor-infiltrating lymphocytes and LNL. In patients with cervical metastases, LNL contained an increased proportion of CD16+ cells. Tumor-involved lymph nodes were not enriched in the CD8+C11b+ subset of T "suppressor" lymphocytes compared with uninvolved lymph nodes. Also, tumor-involved lymph nodes had significantly fewer CD4+ T cells than did uninvolved lymph nodes. In comparison with peripheral blood lymphocytes, freshly isolated tumor-infiltrating lymphocytes and LNL were depleted of cytotoxic effector cells, as indicated by low or absent cytotoxic activity against tumor cell targets. The ability to generate lymphokine-activated killer cells was significantly reduced in LNL in comparison with peripheral blood lymphocytes. In patients with head and neck cancer, depressed local and regional antitumor responses are associated with a deficiency of functional cytotoxic effector cells rather than an increase in suppressor T lymphocytes.