Recently the measurement of cellular DNA content has been focused on knowing the extent of cancer extension and biological behaviour of the tumor cells as well as on producting occurrence of recurrence and the survival time in patients with carcinomas of various organs. And also it is well known that tumor markers such as CEA, CA19-9 and CA72-2 are of great value in predicting recurrence in the follow-up study. It is common that colorectal cancers show well differentiated carcinoma which demonstrates relatively fair prognosis. However, some revealed aggressive and rapid extension of carcinoma, indicating a poor prognosis. The purpose of this study is to certify the significance of the measurement of cellular DNA content for assessing biologic behavior of colorectal cancer in comparison with clinicopathologic factors which have been used for assessment of their prognosis. Development of flow cytometer enabled us to measure the nuclear DNA content with ease, speed and producibility. Furthermore, prevalence of flow cytometric technique makes it possible to know more accurate outcome. When assessed biologically aggressive behavior of tumor cells, potent chemotherapy and extensive surgery are mandatory for improvement of the outcome. It is necessary to search for the method of the accurate assessment of the outcome for patients with carcinomas. The purpose of this study is to clarify the validity of nuclear DNA measurement for assessment of the prognosis in patients with colorectal cancer in comparison with clinicopathologic factors