Forty-three patients with advanced cancer were evaluated for the changes of absolute counts of peripheral blood lymphocytes and lymphocyte subsets during chemotherapy or chemoimmunotherapy. In 27 patients who did not respond to the therapy, whole lymphocytes, T cells, helper/inducer T cells and NK cells decreased significantly in number. In contrast, they showed little decrease in 16 cases responded to the therapy. In situ immunohistochemical analysis of the tumor infiltrating lymphocytes was performed on the carcinoma tissues obtained from 25 gastric cancer patients. T cell infiltration, in which helper/inducer T cells were predominant over suppressor/cytotoxic T cells, and NK cell infiltration were found in most of the tissues comprised various carcinoma types of histology. Furthermore, an analysis of a gastric cancer patient treated with systemic administration of 3 BRMs and intratumoral injection of OK-432 indicated that infiltration of cytotoxic T cells and NK cells augmented by cytokines such as IFN-gamma produced from activated helper/inducer T cells and NK cells. Therefore, it is suggested that movements of helper/inducer T cells and NK cells relate to the response to chemotherapy and participate in prognosis of advanced cancer patients.