The in vitro responsiveness of peripheral blood mononuclear cells (PBMC) T lymphocytes was studied in 81 patients with limited or extended head and neck squamous cell carcinoma (HNSCC), as judged by T, N and T + N stages. Patients included in the study were males below 80 years of age, without auto-immune disease or cachexia, who were not taking any immune-active medication at the time of diagnosis. The patients were divided into groups according to TNM stage T0-2 vs T3-4, N0-1 vs N2-3 or T + N0-3 vs T + N4-7. When cells from patients with early and late stage, according to T, N or T + N stage, were compared, we found a decreased level of mitogen stimulated T-cells and decreased spontaneous proliferation with increasing disease stage. The same was true if the in vitro mitogenesis of T-cells was analysed separately, depending on the laryngeal or oral cavity/pharyngeal origin of the patients' tumours. If the patients were divided into two groups based on N stage, decreased gamma-interferon, and to some extent interleukin (IL-2), but not IL-4 levels, were found to be related to the disease stage.