The proliferative response of T cells cultured with autologous non-T cells is known as the autologous mixed lymphocyte reaction (AMLR). The AMLR in patients with head and neck tumors was found to be significantly decreased in comparison with that in normal donors and patients without evidence of recurrent disease more than 3 years after treatment. Responder T cells in AMLR were CD4+ T cells but not CD8+ T cells. In one patient, AMLR were performed between lymphocytes in condition with tumor burden and those in condition with tumor free by using cryopreserved lymphocytes. T cells in tumor burden state poorly responded to both of these non-T cells. On the other hand, T cell in tumor free state vigorously responded to non-T cells in the same state, but not to non-T cells in tumor burden state. These data indicated that impairment of AMLR in patients with cancer was due to deficit of both responder T cells and autologous stimulator non-T cells.