The prognosis of 141 patients subjected to curative resection for gastric carcinoma was analyzed with special reference to the paracortex, germinal centers and sinus histiocytes in the regional lymph nodes. Five years survival rates of the patients with paracortical and/or germinal center hyperplasia (PH and/or GH) was definitely superior to those without such hyperplasia. This difference was most pronounced in those with moderately advanced stage. The incidence of lymph node metastasis was lower in the patients with PH or GH. The presence of sinus histiocytosis (SH) seemed to be correlated neither with a longer survival nor with lower incidence of lymph node metastasis. No close correlation was found between PH, GH and SH on one hand and histological types of the primary gastric carcinomas on the other. These results suggest that cell mediated and/or humoral immune response may play an important role in host resistance against gastric carcinoma.