The present study was conducted to determine the concomitant immunity in cancer patients by culturing lymph node cells obtained from various cancer patients with the primary cultured tumor cells derived from human cancer and the following results were obtained. 1. The primary cultures were conducted with 42 cases of gastric cancer, 12 of mammary cancer, 8 of cancerous thoracic fluid, 5 of cancerous ascites, 2 of metastatic hepatoma, 2 of thyroid cancer and 7 others. Among them there were 29 cases where the sufficient number of free cells were obtained by the same type of culture so that there were enough viable tumor cells attached on the culture vessel wall to harvest. 2. Effects of autochthonous lymph nodes on human primary cultured cancer cells : From the total of 22 cases comprising 9 cases of gastric cancer, 6 of mammary cancer, 2 of metastatic hepatoma, one of thyroid cancer, 2 of cancerous thoracic fluid and 2 of cancerous ascites, 30 series of cytotoxicity tests were conducted by mixing each of them with autochthonous lymph node cells mainly prepared with lymph nodes obtained at surgical operation. During the mixed culture for the period of 24 hours to 72 hours the cases where the autochthonous lymph node cells had shown anti-proliferative effect on the primary cutured cells amounted to 12/30 cases (70%), and those that showed a proliferative effect instead amounted to 1/30 cases (3.3%). 3. Effects of autochthonous lymph nodes according to their sites on human primary cultured cancer cells : Considering the sites of tumors, the lymph nodes collected were roughly divided into the regional lymph nodes and distant lymph nodes, and looking at their anti-proliferative effect 7/13 cases (54%) of the regional lymph nodes and 14/17 cases (82.4%) of the distant lymph nodes had shown the anti-proliferative effect. 4. Effect of allogeneic lymph nodes on the primary cancer cells derived from human patients: There were 30 lines of mixed cultures of allogeneic lymph node cells and the human primary cultured cancer cells, and of them 11/30 cases (36.7%) showed anti-proliferative effect. By dividing lymph nodes according to cancer patients and non-cancer patients 8/16 cases (50%) in the former had anti-proliferative effect while 3/14 cases (21.4%) in the latter group. From these findings it may be said that there is concomitant immunity established in human cancer and lymph nodes act inhibitorily on tumor. Moreover, most cases having larger tumors are in the terminal stage of cancer, and there can be observed a decrease-disappearance of immunity of regional lymph nodes in such cases.