Although diffuse infiltrative carcinomas of the stomach are mostly composed of anaplastic/mucocellular type, some cases show tubular/trabeculoacinar carcinoma in a large or small part of the tumor. We have subdivided diffuse infiltrative carcinoma into two subtypes, mixed type and pure type, from the viewpoint of the carcinoma's histological structure and lymphatic permeation (LP). The former, or mixed type, includes a tubular/trabeculoacinar element in at least 10% of the tumor tissue, and shows a high tendency for LP. On the other hand, the latter, or pure type, consists almost exclusively of anaplastic/mucocellular carcinoma with a low tendency for LP. No difference in the frequency of LP between males and females was found in the pure type carcinomas, but a significantly higher frequency and grade of LP was observed in males in the mixed type carcinomas. Further, even in the pure type, the LP was rather frequent in people 60 or more years old. Thus, lymphatic permeation seems to be influenced not only by the histological type of the carcinoma but also by sex and age.