Differences between advanced gastric cancer of the medullary type (med.: 138 cases) and the scirrhous type (sci: 164 cases) with regard to the amount of connective tissue that was cancerous have been studied clinicopathologically. A correlation was found between med and liver metastasis, and sci and peritoneal dissemination in metastatic types, whereas no correlation was observed in other factors except between med and a localized type, sci and infiltrating type in gross type. The study of tumorigenicity in nude mice showed remarkable difference between med (86.7%) and sci. (0%). These results indicate that there is definite relationship between the amount of connective tissue and the biological behavior of a gastric cancer.