AbstractLymphocyte activity of patients with gastric cancer and its relation to the stage of cancer were studied. PHA response of lymphocytes from patients with gastric cancer was decreased markedly even in early stage of cancer. The PHA‐stimulated lympho‐cytotoxicity was not impaired in all stages of the disease. Spontaneous lymphocyte‐mediated cytotoxicity showed a tendency to decrease as the cancer stage advanced. The cytotoxic activity of the supernatants from lymphocytes cultured without PHA was significantly high in the advanced stage of gastric c